[opentelemetry-otlp][tonic] Add more information to error message for Unknown status code

[utpilla]

Related to #1923

Changes

Currently, when the OTLP Exporter receives an Unknown code from tonic, the error message isn't helpful. I ran into this issue when I ran the basic-otlp example with the collector container not running on the host machine network. Here is the error message:

OpenTelemetry trace error occurred. Exporter otlp encountered the following error(s): the grpc server returns error (Unknown error): , detailed error message: transport error
Error: Other("[ExportErr(Status { code: Unknown, message: \", detailed error message: transport error\" })]")

I have updated the conversion logic for tonic::Status to Error to add information about the source of the error when we receive an Unkown error. The error message now captures the connection reset issue:

OpenTelemetry trace error occurred. Exporter otlp encountered the following error(s): the grpc server returns error (Unknown error): , detailed error message: transport error tonic::transport::Error(Transport, hyper::Error(Io, Custom { kind: BrokenPipe, error: "stream closed because of a broken pipe" }))
Error: Other("[ExportErr(Status { code: Unknown, message: \", detailed error message: transport error tonic::transport::Error(Transport, hyper::Error(Io, Kind(ConnectionReset)))\" })]")

Please provide a brief description of the changes here.

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.

Project coverage is 74.9%. Comparing base (597327f) to head (801edfa).

Files	Patch %	Lines
opentelemetry-otlp/src/lib.rs	0.0%	10 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1931     +/-   ##
=======================================
- Coverage   75.0%   74.9%   -0.1%     
=======================================
  Files        122     122             
  Lines      20290   20298      +8     
=======================================
- Hits       15222   15221      -1     
- Misses      5068    5077      +9     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.