[Infra] Disallow instance string.Equals methods

[martincostello]

#7196 (comment)

Changes

• Disallow use of string instance Equals() methods and require the static versions be used instead.
• Apply minor refactoring suggested by Visual Studio in files touched.
• Make some comments clearer.

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

❌ Patch coverage is 91.42857% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.50%. Comparing base (44075cd) to head (0a9d8c7).
⚠️ Report is 3 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...enTelemetry/Metrics/StringArrayEqualityComparer.cs	0.00%	2 Missing ⚠️
src/OpenTelemetry/Metrics/Tags.cs	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7210      +/-   ##
==========================================
- Coverage   89.53%   89.50%   -0.03%     
==========================================
  Files         272      272              
  Lines       13345    13343       -2     
==========================================
- Hits        11948    11943       -5     
- Misses       1397     1400       +3     

Flag	Coverage Δ
unittests-Project-Experimental	89.25% <91.42%> (-0.28%)	⬇️
unittests-Project-Stable	89.49% <91.42%> (-0.03%)	⬇️
unittests-Solution	89.27% <91.42%> (-0.11%)	⬇️
unittests-UnstableCoreLibraries-Experimental	40.84% <60.00%> (+0.01%)	⬆️

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

Files with missing lines	Coverage Δ
...nTelemetry.Api/Context/Propagation/B3Propagator.cs	89.83% <100.00%> (ø)
...etryProtocol/Implementation/ExperimentalOptions.cs	95.00% <100.00%> (ø)
...mplementation/ExportClient/OtlpGrpcExportClient.cs	79.31% <100.00%> (ø)
...ementation/Serializer/ProtobufOtlpLogSerializer.cs	99.23% <100.00%> (ø)
...entation/Serializer/ProtobufOtlpTraceSerializer.cs	95.05% <100.00%> (ø)
...enTelemetry.Extensions.Propagators/B3Propagator.cs	88.98% <100.00%> (ø)
...lemetry.Extensions.Propagators/JaegerPropagator.cs	96.03% <100.00%> (ø)
...OpenTelemetry.Shims.OpenTracing/SpanBuilderShim.cs	91.46% <100.00%> (ø)
src/OpenTelemetry.Shims.OpenTracing/SpanShim.cs	85.43% <100.00%> (ø)
...lemetry/Internal/SelfDiagnosticsConfigRefresher.cs	87.73% <100.00%> (+0.69%)	⬆️
... and 3 more

... and 3 files with indirect coverage changes

[Copilot]

Pull request overview

This PR updates repository-wide conventions to disallow instance string.Equals(...) calls (via banned API enforcement) and refactors touched call sites to use the corresponding static string.Equals(...) overloads, along with a few small readability refactors.

Changes:

• Add banned-symbol rules for System.String.Equals(string) and System.String.Equals(string, StringComparison) to enforce static string.Equals(...).
• Replace instance Equals usages across metrics, propagators, OTLP exporter, shims, and shared helpers with static string.Equals(...).
• Apply minor refactors (expression-bodied members, null-conditional dispose) and clarify performance-related comments.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/Shared/StatusHelper.cs	Refactors to expression-bodied switch and replaces instance Equals with static string.Equals.
src/OpenTelemetry/Metrics/Tags.cs	Uses static string.Equals for tag-key comparisons; minor formatting refactor.
src/OpenTelemetry/Metrics/StringArrayEqualityComparer.cs	Uses pattern-matching null checks and static string.Equals for element comparisons.
src/OpenTelemetry/Metrics/Builder/MeterProviderBuilderExtensions.cs	Replaces instance Equals in view matching; refactors Build to expression-bodied form.
src/OpenTelemetry/Internal/SelfDiagnosticsConfigRefresher.cs	Replaces instance Equals for directory compare; simplifies disposal with null-conditional operators.
src/OpenTelemetry.Shims.OpenTracing/SpanShim.cs	Uses static string.Equals for special OpenTracing tag key handling.
src/OpenTelemetry.Shims.OpenTracing/SpanBuilderShim.cs	Uses static string.Equals for OpenTracing tag key comparisons.
src/OpenTelemetry.Extensions.Propagators/JaegerPropagator.cs	Uses static string.Equals for sampled-flag parsing.
src/OpenTelemetry.Extensions.Propagators/B3Propagator.cs	Uses static string.Equals for flags parsing (Recorded decision).
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/Serializer/ProtobufOtlpTraceSerializer.cs	Uses static string.Equals in status tag-value mapping and clarifies perf comment wording.
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/Serializer/ProtobufOtlpLogSerializer.cs	Uses static string.Equals for {OriginalFormat} attribute detection.
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/ExportClient/OtlpGrpcExportClient.cs	Uses static string.Equals for gRPC “no reply detail” detection.
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/ExperimentalOptions.cs	Uses static string.Equals for env-var parsing and refactors disk-path requirement logic.
src/OpenTelemetry.Api/Context/Propagation/B3Propagator.cs	Uses static string.Equals for flags parsing (Recorded decision).
build/BannedSymbols.txt	Adds banned API entries preventing instance string.Equals(...) overload usage.

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