Add status code to OTLP grpc trace log

[ThomsonTan]

The current OTLP grpc exporter logs status_message() on failure which is insufficient for some cases like if the grpc service is not implemented in the server endpoint, status_message() outputs an empty string. Adds status_code in string format to give more information to the log. Following table shows the comparison.

	grpc failure message
Old message	[OTLP TRACE GRPC Exporter] Export() failed with code:
New message	[OTLP TRACE GRPC Exporter] Export() failed with code: "UNIMPLEMENTED" error_message: ""

Changes

Please provide a brief description of the changes here.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[marcalff]

LGTM

[marcalff]

Rebased on main, to resolve CI build failures.

[codecov]

Codecov Report

Merging #1792 (7a0b947) into main (3f0eee6) will increase coverage by 0.08%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1792      +/-   ##
==========================================
+ Coverage   85.71%   85.79%   +0.08%     
==========================================
  Files         171      171              
  Lines        5240     5240              
==========================================
+ Hits         4491     4495       +4     
+ Misses        749      745       -4     

Impacted Files	Coverage Δ
sdk/src/trace/batch_span_processor.cc	91.41% <0.00%> (+0.79%)	⬆️
ext/src/http/client/curl/http_client_curl.cc	81.44% <0.00%> (+1.14%)	⬆️