Use ToOtlpAttribute method for traces

[alanwest]

ToOtlpAttribute method is now used for transforming attributes on all the things: traces, metrics, logs, resources.

There will be a failing test on this PR which will be resolved by merging #3273.

[codecov]

Codecov Report

Merging #3274 (eacc315) into main (d983cb1) will increase coverage by 0.23%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #3274      +/-   ##
==========================================
+ Coverage   85.32%   85.55%   +0.23%     
==========================================
  Files         263      263              
  Lines        9520     9487      -33     
==========================================
- Hits         8123     8117       -6     
+ Misses       1397     1370      -27     

Impacted Files	Coverage Δ
...metryProtocol/Implementation/ActivityExtensions.cs	94.53% <100.00%> (+4.25%)	⬆️
...ZPages/Implementation/ZPagesExporterEventSource.cs	56.25% <0.00%> (-6.25%)	⬇️
...Telemetry/Internal/SelfDiagnosticsEventListener.cs	96.87% <0.00%> (-0.79%)	⬇️
...emetry.Api/Internal/OpenTelemetryApiEventSource.cs	82.35% <0.00%> (+2.94%)	⬆️
...tation/OpenTelemetryProtocolExporterEventSource.cs	86.36% <0.00%> (+9.09%)	⬆️
...xporter.OpenTelemetryProtocol/OtlpTraceExporter.cs	77.27% <0.00%> (+40.90%)	⬆️
...entation/ExportClient/OtlpGrpcTraceExportClient.cs	78.57% <0.00%> (+42.85%)	⬆️