Owin instrumentation

[CodeBlanch]

Resolves #56

Changes

Added OpenTelemetry OWIN Instrumentation. Started from open-telemetry/opentelemetry-dotnet#1472 but made the following changes:

• Moved to contrib
• Dropped the netstandard2.0 target. NuGet was giving me errors about the version being restored for OWIN dependencies on netstandard2.0. I decided to just go with net461. I can't think of a really compelling reason to have netstandard2.0 and we can always add it later if needed.
• Now uses ActivitySource
• Merged the two projects into one
• Added the usual options (Filter, Enrich, RecordException)
• Added an example project

TODOs

• Unit tests

[codecov]

Codecov Report

Merging #156 (050b29f) into main (f277cbe) will increase coverage by 0.15%.
The diff coverage is 80.67%.

❗ Current head 050b29f differs from pull request most recent head 09251a0. Consider uploading reports for the commit 09251a0 to get more accurate results

@@            Coverage Diff             @@
##             main     #156      +/-   ##
==========================================
+ Coverage   78.62%   78.78%   +0.15%     
==========================================
  Files          79       85       +6     
  Lines        1984     2102     +118     
==========================================
+ Hits         1560     1656      +96     
- Misses        424      446      +22     

Impacted Files	Coverage Δ
...y.Contrib.Extensions.AWSXRay/AWSXRayIdGenerator.cs	64.19% <0.00%> (ø)
...n/Implementation/OwinInstrumentationEventSource.cs	26.31% <26.31%> (ø)
...umentation.Owin/TracerProviderBuilderExtensions.cs	83.33% <83.33%> (ø)
...ation.Owin/Implementation/DiagnosticsMiddleware.cs	91.86% <91.86%> (ø)
...ntrib.Instrumentation.Owin/AppBuilderExtensions.cs	100.00% <100.00%> (ø)
...mplementation/OwinInstrumentationActivitySource.cs	100.00% <100.00%> (ø)
...Instrumentation.Owin/OwinInstrumentationOptions.cs	100.00% <100.00%> (ø)

[CodeBlanch]

@SergeyKanzhelev Any free cycles to do a review for me? Trying not to bug the guys working hard to finish up metrics support in SDK.

[alanwest]

LGTM. Just one question about the Propagators option.