OTLP Exporter Enhancements

[vishweshbankwar]

Opening this issue to track work for 1.9.0 release of otlp exporter.

Known issues to consider when planning this effort:

• Exporter.OTLP on .NET Fx relays on deprecated package #4613
• Stabilize OTEL_DOTNET_EXPERIMENTAL_OTLP_EMIT_EVENT_LOG_ATTRIBUTES #5462
• Custom serializer for OTLP exporter #5730
• Adding OpenTelemetry to a native AOT app adds a lot of app size #5785

[rajkumar-rangaraj]

Known issues to consider when planning this effort:

• Exporter.OTLP on .NET Fx relays on deprecated package #4613 - Complete
• Stabilize OTEL_DOTNET_EXPERIMENTAL_OTLP_EMIT_EVENT_LOG_ATTRIBUTES #5462 - Has dependency on spec and can be tracked as separate issue
• Custom serializer for OTLP exporter #5730 - Complete
• Adding OpenTelemetry to a native AOT app adds a lot of app size #5785 - Complete