Rename otel.config.file to otel.experimental.config.file

[jack-berg]

Reflects naming in spec PR: open-telemetry/opentelemetry-specification#3948

The experimental prefix in the name makes it clear to users that the behavior of how file configuration is subject to breaking changes.

This PR removes support for otel.config.file. If it is set, we log a warning.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 91.06%. Comparing base (8937a10) to head (f2b6a2c).
Report is 6 commits behind head on main.

Files	Patch %	Lines
...nfigure/AutoConfiguredOpenTelemetrySdkBuilder.java	50.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6396      +/-   ##
============================================
- Coverage     91.10%   91.06%   -0.05%     
- Complexity     5772     5773       +1     
============================================
  Files           627      627              
  Lines         16852    16858       +6     
  Branches       1720     1722       +2     
============================================
- Hits          15353    15351       -2     
- Misses         1005     1010       +5     
- Partials        494      497       +3     

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