MeterProvider and TracerProvider lifetime guidance added to XML docs

[alanwest]

Follow up from #2848 (review)

[reyang]

Some transient CI failure related to Linux / build-test (netcoreapp3.1):

[xUnit.net 00:00:00.00] xUnit.net VSTest Adapter v2.4.3+1b45f5407b (64-bit .NET Core 3.1.22)
[xUnit.net 00:00:01.11]   Discovering: OpenTelemetry.Instrumentation.AspNetCore.Tests
[xUnit.net 00:00:01.18]   Discovered:  OpenTelemetry.Instrumentation.AspNetCore.Tests
[xUnit.net 00:00:01.18]   Starting:    OpenTelemetry.Instrumentation.AspNetCore.Tests
warn: Microsoft.AspNetCore.DataProtection.KeyManagement.XmlKeyManager[35]
      No XML encryptor configured. Key {49935d13-bbd4-42cf-bc35-789690e0f12f} may be persisted to storage in unencrypted form.
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.BaggageClearedWhenActivityStopped [428 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.StatusIsUnsetOn200Response [[159](https://github.com/open-telemetry/opentelemetry-dotnet/runs/5045597606?check_suite_focus=true#step:8:159) ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.CustomPropagator [90 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.SuccessfulTemplateControllerCallGeneratesASpan(shouldEnrich: False) [40 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.SuccessfulTemplateControllerCallGeneratesASpan(shouldEnrich: True) [30 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.RequestNotCollectedWhenFilterIsApplied [42 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.ExtractContextIrrespectiveOfSamplingDecision(samplingDecision: Drop) [35 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.ExtractContextIrrespectiveOfSamplingDecision(samplingDecision: RecordOnly) [27 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.ExtractContextIrrespectiveOfSamplingDecision(samplingDecision: RecordAndSample) [27 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.AddAspNetCoreInstrumentation_BadArgs [1 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.RequestNotCollectedWhenFilterThrowException [52 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.SuccessfulTemplateControllerCallUsesParentContext [56 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.FilterAndEnrichAreOnlyCalledWhenSampled(samplingDecision: RecordAndSample, shouldFilterBeCalled: True, shouldEnrichBeCalled: True) [23 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.FilterAndEnrichAreOnlyCalledWhenSampled(samplingDecision: RecordOnly, shouldFilterBeCalled: True, shouldEnrichBeCalled: True) [20 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.FilterAndEnrichAreOnlyCalledWhenSampled(samplingDecision: Drop, shouldFilterBeCalled: False, shouldEnrichBeCalled: False) [20 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.BasicTests.ExtractContextIrrespectiveOfTheFilterApplied [31 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.DependencyInjectionConfigTests.TestDIConfig [17 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.EventSourceTest.EventSourceTest_AspNetCoreInstrumentationEventSource [4 ms]
fail: Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[1]
      An unhandled exception has occurred while executing the request.
System.Exception: exception description
   at OpenTelemetry.Instrumentation.AspNetCore.Tests.IncomingRequestsCollectionsIsAccordingToTheSpecTests.TestCallbackMiddlewareImpl.ProcessAsync(HttpContext context) in /home/runner/work/opentelemetry-dotnet/opentelemetry-dotnet/test/OpenTelemetry.Instrumentation.AspNetCore.Tests/IncomingRequestsCollectionsIsAccordingToTheSpecTests.cs:line [181](https://github.com/open-telemetry/opentelemetry-dotnet/runs/5045597606?check_suite_focus=true#step:8:181)
   at TestApp.AspNetCore._3._1.CallbackMiddleware.InvokeAsync(HttpContext context) in /home/runner/work/opentelemetry-dotnet/opentelemetry-dotnet/test/TestApp.AspNetCore.3.1/CallbackMiddleware.cs:line 34
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
warn: Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[2]
      The response has already started, the error page middleware will not be executed.
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.MetricTests.AddAspNetCoreInstrumentation_BadArgs [< 1 ms]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.MetricTests.RequestMetricIsCaptured [1 s]
  Passed OpenTelemetry.Instrumentation.AspNetCore.Tests.IncomingRequestsCollectionsIsAccordingToTheSpecTests.SuccessfulTemplateControllerCallGeneratesASpan(urlPath: "/api/values", userAgent: "user-agent", statusCode: 503, reasonPhrase: "503", recordException: False) [36 ms]
fail: Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[1]
      An unhandled exception has occurred while executing the request.
System.Exception: exception description
   at OpenTelemetry.Instrumentation.AspNetCore.Tests.IncomingRequestsCollectionsIsAccordingToTheSpecTests.TestCallbackMiddlewareImpl.ProcessAsync(HttpContext context) in /home/runner/work/opentelemetry-dotnet/opentelemetry-dotnet/test/OpenTelemetry.Instrumentation.AspNetCore.Tests/IncomingRequestsCollectionsIsAccordingToTheSpecTests.cs:line 181
   at TestApp.AspNetCore._3._1.CallbackMiddleware.InvokeAsync(HttpContext context) in /home/runner/work/opentelemetry-dotnet/opentelemetry-dotnet/test/TestApp.AspNetCore.3.1/CallbackMiddleware.cs:line 34
   at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware.Invoke(HttpContext context)
warn: Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddleware[2]
      The response has already started, the error page middleware will not be executed.

[alanwest]

This too

https://github.com/open-telemetry/opentelemetry-dotnet/runs/5045597606?check_suite_focus=true

Failed OpenTelemetry.Exporter.Prometheus.Tests.PrometheusExporterHttpServerTests.PrometheusExporterHttpServerIntegration [80 ms]
  Error Message:
   System.Net.Http.HttpRequestException : Connection refused
---- System.Net.Sockets.SocketException : Connection refused
  Stack Trace:
     at System.Net.Http.ConnectHelper.ConnectAsync(String host, Int32 port, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPool.ConnectAsync(HttpRequestMessage request, Boolean allowHttp2, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPool.CreateHttp11ConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPool.GetHttpConnectionAsync(HttpRequestMessage request, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken)
   at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
   at System.Net.Http.HttpClient.FinishSendAsyncBuffered(Task`1 sendTask, HttpRequestMessage request, CancellationTokenSource cts, Boolean disposeCts)
   at OpenTelemetry.Exporter.Prometheus.Tests.PrometheusExporterHttpServerTests.PrometheusExporterHttpServerIntegration() in /home/runner/work/opentelemetry-dotnet/opentelemetry-dotnet/test/OpenTelemetry.Exporter.Prometheus.Tests/PrometheusExporterHttpServerTests.cs:line 98

[codecov]

Codecov Report

Merging #2850 (1f8275c) into main (3833a4f) will decrease coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #2850      +/-   ##
==========================================
- Coverage   83.76%   83.74%   -0.03%     
==========================================
  Files         250      250              
  Lines        8882     8882              
==========================================
- Hits         7440     7438       -2     
- Misses       1442     1444       +2     

Impacted Files	Coverage Δ
src/OpenTelemetry/Sdk.cs	100.00% <ø> (ø)
...ter.ZPages/Implementation/ZPagesActivityTracker.cs	97.14% <0.00%> (-2.86%)	⬇️
...Telemetry/Internal/SelfDiagnosticsEventListener.cs	96.87% <0.00%> (-0.79%)	⬇️