Graduate experimental-grpc-retry and experimental-http-retry feature flags to stable

[scottgerring]

Summary

The OTLP exporter has two feature flags gating retry behaviour:

• experimental-grpc-retry — retry with exponential backoff for gRPC/tonic exports
• experimental-http-retry — retry with exponential backoff for HTTP exports

The underlying retry behaviour is described as a MUST in the OTLP exporter specification. Since the spec considers this stable and required, these flags should not remain experimental — the retry logic should be on by default and the experimental-* feature gates removed.

[SATVIKsynopsis]

Hi, I would like to work on this issue. I have been contributing to the OTLP HTTP exporter in this repo and am familiar with the retry code. I'll start by identifying all places where the experimental feature flags are used and work on making retry the default behavior.

[cijothomas]

@SATVIKsynopsis Stabilizing retry is blocked on stabilizing runtime abstraction - #2643 There are couple of proposals open for discussion on this by Scott already. Please help reviewing them, and that'll indirectly help with the retry stabilization!