otelhttp: deprecate WithPublicEndpoint in favor of WithPublicEndpointFn (#8133)

[n2p5]

Note: This is my first contribution to open-telemetry/oepntelemetry-go-contrib. I found this issue from the "good first issue" label, so if I've messed anything up or I skipped a step, let me know!

This addresses Issue: #8133

WithPublicEndpoint now delegates to WithPublicEndpointFn to reduce code duplication and maintenance burden. The PublicEndpoint bool field has been removed from the config and middleware structs in favor of using only PublicEndpointFn.

This simplifies the implementation to a single code path while maintaining full backward compatibility.

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: dmathieu / name: Damien Mathieu (eca5dca)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.8%. Comparing base (471b3d7) to head (eca5dca).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #8152     +/-   ##
=======================================
- Coverage   81.8%   81.8%   -0.1%     
=======================================
  Files        194     194             
  Lines      13380   13377      -3     
=======================================
- Hits       10954   10951      -3     
  Misses      2029    2029             
  Partials     397     397             

Files with missing lines	Coverage Δ
instrumentation/net/http/otelhttp/config.go	81.5% <100.0%> (-0.6%)	⬇️
instrumentation/net/http/otelhttp/handler.go	92.6% <100.0%> (-0.1%)	⬇️

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[n2p5]

Thank you, @dmathieu and @flc1125. Is there anything else you need me to do on my side for this? I merged the latest changes from main to ensure we don't have any code drift. However, other than that, this needs to be authorized to rerun the rest of the pipeline.