refactor: Align global trace with metrics

[andrzejressel]

Changes

This pull requests align setting global tracer with settings global metrics - mem::replace was replaced with mutable assignment and old tracer is no longer returned.

In addition failure to set global tracer does not crash program anymore - it will return noop and log error - like with global metrics

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: andrzejressel / name: ​Andrzej Ressel (74ea482, 8c34173, 58781b6, 178f1b1, 2a0586d)
• ✅ login: cijothomas / name: Cijo Thomas (6cb6a16)
• ✅ login: lalitb / name: Lalit Kumar Bhasin (51070cf)

[Copilot]

Pull Request Overview

This PR aligns the behavior of the global tracer provider with the global metrics provider by modifying the set_tracer_provider function to not return the previous provider and adding error handling that returns noop implementations with logging instead of panicking.

• Changed set_tracer_provider return type from GlobalTracerProvider to unit
• Added graceful error handling for RwLock poisoning with logging instead of panics
• Replaced mem::replace with direct assignment for consistency with metrics implementation

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
opentelemetry/src/global/trace.rs	Modified tracer provider functions to handle errors gracefully and align API with metrics
opentelemetry/CHANGELOG.md	Added changelog entry documenting the breaking API change

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 13 lines in your changes missing coverage. Please review.

Project coverage is 80.2%. Comparing base (c5fde17) to head (6cb6a16).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
opentelemetry/src/global/trace.rs	0.0%	11 Missing ⚠️
opentelemetry-sdk/src/trace/runtime_tests.rs	0.0%	2 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3078   +/-   ##
=====================================
  Coverage   80.1%   80.2%           
=====================================
  Files        126     126           
  Lines      21949   21949           
=====================================
+ Hits       17603   17604    +1     
+ Misses      4346    4345    -1     

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