[OpenTelemetry.Extensions] Trace RateLimitingSampler reject non-positive values

[ysolomchenko]

Fixes # N/A
Design discussion issue # N/A

Found by Codex analysis

Changes

RateLimitingSampler reject non-positive maxTracesPerSecond values instead of creating an invalid internal rate limiter state.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.83%. Comparing base (25a64cf) to head (2d1b487).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4127   +/-   ##
=======================================
  Coverage   72.83%   72.83%           
=======================================
  Files         461      461           
  Lines       18215    18217    +2     
=======================================
+ Hits        13267    13269    +2     
  Misses       4948     4948           

Flag	Coverage Δ
unittests-Extensions	90.74% <100.00%> (+0.08%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...nTelemetry.Extensions/Trace/RateLimitingSampler.cs	100.00% <100.00%> (ø)

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