internal_config feature removal

[milyin]

Description

What does this PR do?

The PR removes internal_config feature usage from the codebase

Why is this change needed?

It was decided to remove the "internal_config" feature in #1655 and the removal was done on #1939.

That PR was reverted in #2031 because it caused CI failure on API compatibility check which is hard to reconfigure.

This PR makes the removal in a safe way: it removes usage of internal_config feature, but keeps it in Cargo.toml as a dummy entry, keeping the API formally compatible,

To finish the fix it it's necessary to temporary disable the check, make release with changed API (without internal_config feature) and restore the check, pointing to new release. This can be done separately.

Related Issues

Partially fixes #1655
Contains the reverted #1939 with changes

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🏷️ Label-Based Checklist

Based on the labels applied to this PR, please complete these additional requirements:

Labels: enhancement

✨ Enhancement Requirements

Since this PR enhances existing functionality:

• Enhancement scope documented - Clear description of what is being improved
• Minimum necessary code - Implementation is as simple as possible, doesn't overcomplicate the system
• Backwards compatible - Existing code/APIs still work unchanged
• No new APIs added - Only improving existing functionality
• Tests updated - Existing tests pass, new test cases added if needed
• Performance improvement measured - If applicable, before/after metrics provided
• Documentation updated - Existing docs updated to reflect improvements
• User impact documented - How users benefit from this enhancement

Remember: Enhancements should not introduce new APIs or breaking changes.

Instructions:

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.88%. Comparing base (f9d6b39) to head (492bce6).
⚠️ Report is 8 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2352   +/-   ##
=======================================
  Coverage   71.88%   71.88%           
=======================================
  Files         387      387           
  Lines       61972    61961   -11     
=======================================
- Hits        44546    44540    -6     
+ Misses      17426    17421    -5     

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