OTLP endpoint issues

[ying-jeanne]

This ticket is to track all left works to be done in order to support otlp endpoint

bugs

• Add a limit on max remote write request samples #6935
• OTLP/HTTP Endpoint Invalid Temporality When Using AggregationTemporality.DELTA #6696

Tasks

Beta Give feedback

1. otlp: improve mimir error message for otlp endpoint, in order to give better instruction on collector config #8240
   area/opentelemetry +1
2. Mimir rejects samples when exemplar is non-compliant #8210
   area/opentelemetry bug component/distributor +3
   
3. otlp: Mimir's OTLP endpoint to return marshalled proto bytes as response body #8185
   area/opentelemetry bug +2
   
4. otlp: Mimir's OTLP endpoint write request size limit should be configured in the same unit as the metrics producers #8260
   area/opentelemetry +1
5. otlp: Add metrics to track samples per batch for otlp request #8269
   +0
   
6. mapping no retryable 5xx errors to retryable error in otlp handler #8310
   area/opentelemetry bug +2