Add benchmark numbers and remove invalid case

[cijothomas]

Removed the benchmark using CustomProperty. OTel does not use it ever.
Added numbers for quick reference.

[codecov]

Codecov Report

Merging #3848 (d9cc7f5) into main (131b350) will decrease coverage by 0.08%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3848      +/-   ##
==========================================
- Coverage   87.47%   87.39%   -0.09%     
==========================================
  Files         280      280              
  Lines       10765    10765              
==========================================
- Hits         9417     9408       -9     
- Misses       1348     1357       +9     

Impacted Files	Coverage Δ
src/OpenTelemetry/Logs/Pool/LogRecordSharedPool.cs	78.94% <0.00%> (-21.06%)	⬇️
...porter.OpenTelemetryProtocol/OtlpMetricExporter.cs	72.72% <0.00%> (-13.64%)	⬇️
...tation/OpenTelemetryProtocolExporterEventSource.cs	85.00% <0.00%> (-10.00%)	⬇️
...metryProtocol/Implementation/ActivityExtensions.cs	96.21% <0.00%> (+1.08%)	⬆️
...emetry.Api/Internal/OpenTelemetryApiEventSource.cs	82.35% <0.00%> (+2.94%)	⬆️
...lementation/SqlClientInstrumentationEventSource.cs	75.00% <0.00%> (+4.16%)	⬆️

[CodeBlanch]

LGTM