[CONFIGURATION] Programmatic configuration use case tests and fixes

[dbarker]

Contributes to #4134

Adds unit and integration tests for the programmatic configuration use case and fixes issues found.

Changes

• Fixes missing initialization of SdkBuilder and ConfiguredSdk members.
• Fixes issues with SdkBuilder for the programmatic configuration use case
  • Set the default sampler to parent based always on when the sampler config is null
  • Set the default parent based root sampler to always_on when configured root sampler is null
  • Set the default metric stream aggregation when the aggregation config is null
  • Set export_timeout for batch processors. (export timeout is unused in the SDK but should be configured to avoid being set by the environment variable)
• SdkBuilder test for CreateParentBasedSampler has been added
• ConfiguredSdk tests for the core interface (Global Logger/Install/Uninstall) have been added
• Programmatic Configuration integration tests have been added to verify the configured SDK has the expected components and exports expected signal data

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

❌ Patch coverage is 80.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.16%. Comparing base (3e4296e) to head (b5c19ec).

Files with missing lines	Patch %	Lines
sdk/src/configuration/sdk_builder.cc	80.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4243      +/-   ##
==========================================
+ Coverage   78.15%   81.16%   +3.01%     
==========================================
  Files         440      444       +4     
  Lines       18736    18800      +64     
==========================================
+ Hits        14642    15257     +615     
+ Misses       4094     3543     -551     

Files with missing lines	Coverage Δ
...e/opentelemetry/sdk/configuration/configured_sdk.h	100.00% <ø> (+100.00%)	⬆️
sdk/src/configuration/sdk_builder.cc	45.05% <80.00%> (+40.05%)	⬆️

... and 39 files with indirect coverage changes

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[marcalff]

LGTM.

Thanks for all the tests.