OTLPLogExporter bug fix to handle null EventName

[cijothomas]

Fixes #2870

Changes

Apart from null exception fix, this also adds a very basic test for OTLP LogRecord. This is very basic, and a step1 towards adding proper tests (currently there are no tests for OTLP Logs)

[codecov]

Codecov Report

Merging #2871 (b648576) into main (fe7b917) will increase coverage by 0.34%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #2871      +/-   ##
==========================================
+ Coverage   83.76%   84.10%   +0.34%     
==========================================
  Files         250      245       -5     
  Lines        8882     8777     -105     
==========================================
- Hits         7440     7382      -58     
+ Misses       1442     1395      -47     

Impacted Files	Coverage Δ
...etryProtocol/Implementation/LogRecordExtensions.cs	56.66% <100.00%> (+56.66%)	⬆️
....TelemetryHttpModule/TelemetryHttpModuleOptions.cs	0.00% <0.00%> (-90.00%)	⬇️
...emetry.Api/Internal/OpenTelemetryApiEventSource.cs	76.47% <0.00%> (-5.89%)	⬇️
....AspNet.TelemetryHttpModule/TelemetryHttpModule.cs	0.00% <0.00%> (-5.27%)	⬇️
...umentation.AspNet/Implementation/HttpInListener.cs
...rumentation.AspNet/AspNetInstrumentationOptions.cs
...Implementation/AspNetInstrumentationEventSource.cs
...ry.Instrumentation.AspNet/AspNetInstrumentation.cs
...entation.AspNet/TracerProviderBuilderExtensions.cs
...metryProtocol/Implementation/ActivityExtensions.cs	86.75% <0.00%> (+0.91%)	⬆️
... and 6 more

[glucaci]

There are any plans to release this fix soon ?