[OpenTelemetry] Remove vendored EnvironmentVariablesConfigurationProvider

[stevejgordon]

Fixes #7141
Contributes to #6380 as a pre-requisite simplification

Changes

• Remove vendored EnvironmentVariablesConfigurationProvider.
• Update dependencies to use Microsoft.Extensions.Configuration.EnvironmentVariables.
• Add basic E2E test to validate existing ENV VAR behaviour continues to function.

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)

[martincostello]

The change seems OK to me from a code perspective, but I defer to the other maintainers for background on why this was done in the first place that might cause issues (e.g. the additional dependencies for opentelemetry-dotnet-instrumentation).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.64%. Comparing base (bc1fbe6) to head (2bb7937).
⚠️ Report is 68 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7146      +/-   ##
==========================================
+ Coverage   89.59%   89.64%   +0.05%     
==========================================
  Files         272      272              
  Lines       13376    13376              
==========================================
+ Hits        11984    11991       +7     
+ Misses       1392     1385       -7     

Flag	Coverage Δ
unittests-UnstableCoreLibraries-Experimental	40.96% <ø> (ø)

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see 1 file with indirect coverage changes

[stevejgordon]

Yeah if the driver is dependency reduction, then we may need to instead consider if we want a sync mechanism for the vendored code intead. I know the instrumentation team were doing work to improve dependency issues, so this may now be suitable.

[Kielek]

@open-telemetry/dotnet-instrumentation-approvers perspective:
after changes in 1.15.0 this additional dependency should not be a problem any longer. Even for .NET versions. It will increase a bit the distribution size.

I would not block this change only for AutoInstrumentation.

[Kielek]

@martincostello, as I remember you have implemented scope tools for testing env vars. Can it be used instead of adding collections?

[martincostello]

If EnvironmentVariableScope is being used we shouldn't need to use it, unless there's a lot of parallelism going on.

[github-actions]

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[stevejgordon]

I can update the tests if we still want to consider this change? I guess we need a final position from the @open-telemetry/dotnet-maintainers on taking this dependency within the SDK.

[github-actions]

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