BatchProcessor -Testing #2512
Description
- Need to see how best to perf test the BatchProcessor's throughput. Some prior work from .NET - https://github.com/open-telemetry/opentelemetry-dotnet/pull/3355/files and [Don't merge] Stress test for CircularBuffer opentelemetry-dotnet#1086
- Add unit test so it is relatively easy to catch issues like Fix BatchLogProcessor #2510