add option for public endpoint to gRPC

[jan-xyz]

Related: #7406

This adds the option to mark endpoints as public, it is in line with the implementation of otelhttp.

[dashpole]

looks good. Just needs unit tests for config and for the handler

[jan-xyz]

hey, thank you for the fast response. I added tests, I based them on the otelhttp tests again to keep them both close. There were no existing tests for this part of the code so I hope this works.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.3%. Comparing base (64d8e65) to head (69593bc).
Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #7407   +/-   ##
=====================================
  Coverage   82.2%   82.3%           
=====================================
  Files        205     205           
  Lines      17949   17967   +18     
=====================================
+ Hits       14768   14795   +27     
+ Misses      2743    2735    -8     
+ Partials     438     437    -1     

Files with missing lines	Coverage Δ
...entation/google.golang.org/grpc/otelgrpc/config.go	92.0% <100.0%> (+10.4%)	⬆️
...n/google.golang.org/grpc/otelgrpc/stats_handler.go	98.7% <100.0%> (+<0.1%)	⬆️

... and 1 file with indirect coverage changes

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[dmathieu]

Please don't rebase your branch every time. Merge commits make our reviews much easier.

[jan-xyz]

sorry for the many rebases, I only wanted to fix the merge conflict with main. I hope I didn't complicate things for the PR?