[TEST] Add Windows max macro regression test for OTLP public headers

[ThomsonTan]

Follow up for the comment #3861 (comment)

Changes

• Adds a new regression test in otlp_windows_max_macro_compile_test.cc that defines a Windows-style max macro before including OTLP public headers.
• Prevents recurrence of the Windows/MSVC include-order failure reported in issue v1.25 regression: Build break on Windows with Visual Studio 2022 #3861; no runtime behavior changes, test-only coverage improvement.

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

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.99%. Comparing base (717cfc9) to head (9f66370).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3865   +/-   ##
=======================================
  Coverage   89.99%   89.99%           
=======================================
  Files         225      225           
  Lines        7170     7170           
=======================================
  Hits         6452     6452           
  Misses        718      718           

see 2 files with indirect coverage changes

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[marcalff]

@ThomsonTan

What this new test will do, is prevent similar bugs to be introduced again in otlp_http_exporter_options.h.

It will not prevent another similar bug to appear in another header file.

Suggestion: implement a new CI check script, similar to tools/check_copyright.sh, that looks for known dangerous coding pattern.

A script running grep -w "max(" on all the source code will pick up the next break.