PoC: Configuration\CompositeResolver and SPI discovery

[ChrisLightfootWild]

Proof of concept, to cover the use-case where multi-application installs operate on shared-infra and wish to provide their own configuration.

See #1436.

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Any suggestions on the best way to approach adding tests for these optional dependencies?

[codecov[bot]]

Codecov Report

:x: Patch coverage is 3.63636% with 53 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 68.28%. Comparing base (e54a43d) to head (40acb23). :warning: Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...onfiguration/Resolver/SdkConfigurationResolver.php	0.00%	11 Missing :warning:
src/Config/SDK/Configuration.php	0.00%	10 Missing :warning:
src/Config/SDK/Instrumentation.php	0.00%	10 Missing :warning:
...tion/Environment/Adapter/SymfonyDotenvProvider.php	0.00%	9 Missing :warning:
...on/Environment/Adapter/VlucasPhpdotenvProvider.php	0.00%	7 Missing :warning:
...ig/SDK/Configuration/Environment/LazyEnvSource.php	0.00%	6 Missing :warning:

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1523      +/-   ##
============================================
- Coverage     68.76%   68.28%   -0.48%     
- Complexity     2857     2868      +11     
============================================
  Files           425      429       +4     
  Lines          8704     8740      +36     
============================================
- Hits           5985     5968      -17     
- Misses         2719     2772      +53     

Flag	Coverage Δ
8.1	?
8.2	?
8.3	?
8.4	?
8.5	68.28% <3.63%> (-0.28%)	:arrow_down:

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

Files with missing lines	Coverage Δ
...ommon/Configuration/Resolver/CompositeResolver.php	100.00% <100.00%> (ø)
...mon/Configuration/Resolver/EnvironmentResolver.php	100.00% <100.00%> (ø)
...K/Common/Configuration/Resolver/PhpIniResolver.php	100.00% <ø> (ø)
...ig/SDK/Configuration/Environment/LazyEnvSource.php	0.00% <0.00%> (ø)
...on/Environment/Adapter/VlucasPhpdotenvProvider.php	0.00% <0.00%> (ø)
...tion/Environment/Adapter/SymfonyDotenvProvider.php	0.00% <0.00%> (ø)
src/Config/SDK/Configuration.php	0.00% <0.00%> (ø)
src/Config/SDK/Instrumentation.php	0.00% <0.00%> (ø)
...onfiguration/Resolver/SdkConfigurationResolver.php	0.00% <0.00%> (ø)

... and 6 files with indirect coverage changes

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[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[brettmc]

This looks pretty solid now, would you like to rebase and we can get it merged @ChrisLightfootWild ?