Progressive plan to improve OTLP and OTAP receivers/exporters + Ack/Nack system

[lquerel]

This plan aims to break down #1357 and #1382 into smaller steps that are easier to review and validate progressively with our continuous benchmark system.

• OtlpProtoBytes - Use bytes::Bytes for OTLP payloads across pdata/otap #1473

  • Convert Vec<u8> to bytes::Bytes as preparatory work for upcoming changes

• gRPC Shared Settings (across OTLP and OTAP) - #1470

  • GrpcClientSettings
  • GrpcServerSettings

• OTLP Exporter

  • Support multiple client connections
  • Improve gRPC settings
  • Improve metrics

• OTAP Exporter

  • Support multiple client connections
  • Improve gRPC settings
  • Improve metrics

• OTLP Receiver

  • Integrate ack registry v2
  • Improve gRPC settings
  • Improve metrics

• OTAP Receiver

  • Integrate ack registry v2
  • Improve gRPC settings
  • Improve metrics

• OTel Receiver (experimental h2 based gRPC server)