module: emit experimental warning for module.register()

[GeoffreyBooth]

Alternative to #62401. Adds an experimental warning to module.register(), without deprecating it.

[nodejs-github-bot]

Review requested:

• @nodejs/loaders

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.70%. Comparing base (7ffbb76) to head (792a8bf).
⚠️ Report is 20 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62518      +/-   ##
==========================================
- Coverage   89.70%   89.70%   -0.01%     
==========================================
  Files         692      694       +2     
  Lines      214039   214228     +189     
  Branches    41064    41113      +49     
==========================================
+ Hits       192010   192178     +168     
- Misses      14091    14112      +21     
  Partials     7938     7938              

Files with missing lines	Coverage Δ
lib/internal/modules/esm/loader.js	98.78% <100.00%> (+0.01%)	⬆️

... and 34 files with indirect coverage changes

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[aduh95]

That API is no longer experimental