Emit warning when TraceIdRatioBasedSampler is used as child sampler

[Gosling-dude]

What does this change do?

• Emits a WARNING when TraceIdRatioBasedSampler is configured as a child sampler via ParentBasedSamplerBuilder.
• Warning is logged once at configuration time only.
• No runtime or sampling behavior is changed.

Why is this needed?

• Required by the OpenTelemetry trace SDK specification.
• Using TraceIdRatioBasedSampler as a child sampler can lead to unexpected behavior.

Implementation notes:

• Warning logic lives only in ParentBasedSamplerBuilder.
• ParentBasedSampler remains behavior-only with no logging or side effects.

How was this tested?

• ./gradlew :sdk:trace:test
• ./gradlew spotlessCheck

Closes #7790

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: Gosling-dude / name: Sumit Chauhan (49677d9, 4af9078, 64e09bc, db30494, ef83131)

[codecov]

Codecov Report

❌ Patch coverage is 69.23077% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.07%. Comparing base (1093571) to head (64e09bc).

Files with missing lines	Patch %	Lines
.../sdk/trace/samplers/ParentBasedSamplerBuilder.java	69.23%	0 Missing and 4 partials ⚠️

❌ Your patch check has failed because the patch coverage (69.23%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #7937      +/-   ##
============================================
- Coverage     90.09%   90.07%   -0.03%     
- Complexity     7432     7437       +5     
============================================
  Files           834      834              
  Lines         22537    22550      +13     
  Branches       2236     2236              
============================================
+ Hits          20304    20311       +7     
- Misses         1532     1533       +1     
- Partials        701      706       +5     

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