Refactor exporter - step 5

[reyang]

This is a follow up PR of #1078.

Changes

• Added Ingress and Egress internal properties to the circular buffer, which would be useful for internal logging.
• Integrated circular buffer to BatchExportActivityProcessor.

For significant contributions please make sure you have completed the following items:

• Design discussion issue #
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #1087 into master will decrease coverage by 0.15%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #1087      +/-   ##
==========================================
- Coverage   76.17%   76.01%   -0.16%     
==========================================
  Files         225      225              
  Lines        6199     6208       +9     
==========================================
- Hits         4722     4719       -3     
- Misses       1477     1489      +12     

Impacted Files	Coverage Δ
src/OpenTelemetry/Internal/CircularBuffer.cs	0.00% <0.00%> (ø)
...penTelemetry/Trace/BatchExportActivityProcessor.cs	0.00% <0.00%> (ø)
...us/Implementation/PrometheusExporterEventSource.cs	63.63% <0.00%> (-9.10%)	⬇️
...nTelemetry/Internal/OpenTelemetrySdkEventSource.cs	79.41% <0.00%> (-2.95%)	⬇️

[CodeBlanch]

It is probably more .NET-y to use AddedCount, RemovedCount, and DroppedCount (or simiar) as the names for ingress, egress, & regress.

[reyang]

It is probably more .NET-y to use AddedCount, RemovedCount, and DroppedCount (or similar) as the names for ingress, egress, & regress.

I've updated the names. Please take a look.

Initially I was thinking to use these abstract names to unify the queue/process/exporter (e.g. queue would have AddedCount/EnqueuedCount, RemovedCount/DequeuedCount; processor would have ReceivedCount, ProcessedCount and DroppedCount; exporter would have ReceivedCount, DroppedCount (in case of bad data) and ExportedCount).