module: add module.entrypoint

[mcollina]

Adds module.entrypoint to node:module: the resolved URL string of the entry point of the current thread.

The semantics follow require.main and import.meta.main (thread-scoped): inside a worker thread it is the URL of the script the worker was started with, not the entry point of the process. This complements #64800, which exposes the process-wide entry point inherited by workers.

• Works regardless of whether the entry point is CommonJS or ESM.
• undefined for --eval, the REPL, STDIN input, and eval: true workers; set to the data: URL for data URL workers.
• The value is fully resolved: extension searching is applied and symlinks are followed (unless --preserve-symlinks-main), so it matches require.main.filename / the entry point's import.meta.url rather than process.argv[1].

Refs: #51840
Refs: #64800

[nodejs-github-bot]

Review requested:

• @nodejs/loaders

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.15%. Comparing base (a7d16a8) to head (b6075b5).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #64903      +/-   ##
==========================================
+ Coverage   90.13%   90.15%   +0.01%     
==========================================
  Files         746      746              
  Lines      242893   242925      +32     
  Branches    45769    45777       +8     
==========================================
+ Hits       218935   219006      +71     
+ Misses      15444    15399      -45     
- Partials     8514     8520       +6     

Files with missing lines	Coverage Δ
lib/internal/main/worker_thread.js	94.37% <100.00%> (+0.01%)	⬆️
lib/internal/modules/helpers.js	98.96% <100.00%> (+0.02%)	⬆️
lib/internal/modules/run_main.js	97.71% <100.00%> (+0.06%)	⬆️
lib/module.js	100.00% <100.00%> (ø)

... and 25 files with indirect coverage changes

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