[12.x backport] module: remove experimental modules warning

[guybedford]

This backports the PR with the removal of the experimental warning from #31974.

This seems important as many users are unaware the 12.x implementation provides the same stable base-level modules functionality.

It would be nice to get the approvals here in the mean time, but this should probably only land once the two previously left out backports from the last 12 release have landed:

• CJS exports [v12.x backport] CJS exports detection #35405
• CJS module lexer performance patch module: update to [email protected] #35501
• The exports pattern commit from [12.x] modules backports #35385 which was bumped from the last release
• Documentation backports [v12 backport] ESM (named exports for CJS, package.json docs, subpath export patterns, warning removal) #35757

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

[guybedford]

Superseded by #35757.