Zipkin Exporter fixes

[cijothomas]

Part of #2872

Changes

Zipkin Exporter modified to not throw in Export method
Jaeger Exporter modified to use SuppressInstrumentationScope to prevents its internal operations from being instrumented. (More relevant since http support added, but even without it, this is following the Exporter recommendations from https://github.com/open-telemetry/opentelemetry-dotnet/tree/main/docs/trace/extending-the-sdk#exporter)

[codecov]

Codecov Report

Merging #2935 (f4af392) into main (72ade32) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main    #2935   +/-   ##
=======================================
  Coverage   83.86%   83.86%           
=======================================
  Files         254      254           
  Lines        8941     8941           
=======================================
  Hits         7498     7498           
  Misses       1443     1443           

Impacted Files	Coverage Δ
...rc/OpenTelemetry.Exporter.Zipkin/ZipkinExporter.cs	88.42% <100.00%> (ø)
...Telemetry/Internal/SelfDiagnosticsEventListener.cs	96.87% <0.00%> (-0.79%)	⬇️
...nTelemetry/Internal/OpenTelemetrySdkEventSource.cs	72.22% <0.00%> (+0.92%)	⬆️