[Infra] Fix new code analysis warnings

[martincostello]

Changes

Cherry-pick fixes for new code analysis warnings identified by the .NET 11 preview 3 SDK in #6899.

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 88.73%. Comparing base (e0948d0) to head (1dbdd25).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7098      +/-   ##
==========================================
- Coverage   88.79%   88.73%   -0.07%     
==========================================
  Files         270      270              
  Lines       12928    12927       -1     
==========================================
- Hits        11480    11471       -9     
- Misses       1448     1456       +8     

Flag	Coverage Δ
unittests-Project-Experimental	88.69% <100.00%> (-0.09%)	⬇️
unittests-Project-Stable	88.65% <100.00%> (-0.09%)	⬇️

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

Files with missing lines	Coverage Δ
...lemetry.Extensions.Propagators/JaegerPropagator.cs	95.23% <ø> (-0.05%)	⬇️
.../OpenTelemetry/Internal/BatchExportThreadWorker.cs	82.92% <100.00%> (ø)
...ernal/PeriodicExportingMetricReaderThreadWorker.cs	75.47% <ø> (ø)

... and 3 files with indirect coverage changes

[Copilot]

Pull request overview

Cherry-picks small code tweaks to address new .NET 11 preview 3 SDK code analysis warnings across tests, benchmarks, and a few internal/runtime components.

Changes:

• Updates test/benchmark code to satisfy newer analyzer expectations (e.g., collection expressions, local function formatting).
• Adjusts a unit test timeout pattern using WaitAsync on modern TFMs while keeping compatibility for older targets.
• Makes minor internal code cleanups (e.g., switch exhaustiveness, thread naming, null-forgiveness removal).

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/OpenTelemetry.Tests/Logs/BatchLogRecordExportProcessorTests.cs	Uses collection expressions for list initialization in tests.
test/OpenTelemetry.Tests/Internal/InterlockedHelperTests.cs	Refines timeout handling to avoid hangs and align with newer analyzers across TFMs.
test/Benchmarks/Context/Propagation/BaggagePropagatorBenchmarks.cs	Rewrites a local function body to satisfy updated analyzer/style expectations.
src/OpenTelemetry/Internal/PeriodicExportingMetricReaderThreadWorker.cs	Adds an explicit default switch case for analyzer satisfaction (no functional change).
src/OpenTelemetry/Internal/BatchExportThreadWorker.cs	Adjusts nameof usage in thread naming to avoid generic-type analyzer warnings.
src/OpenTelemetry.Extensions.Propagators/JaegerPropagator.cs	Removes redundant null-forgiveness/conditional compilation around a non-nullable parameter.

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