[v8.x-backport] n-api: mark thread-safe function as stable
Remove NAPI_EXPERIMENTAL guard from around N-API thread-safe function APIs.
Unlike in later versions of Node.js in this version the NAPI_EXPERIMENTAL
guard cannot be replaced with #if NAPI_VERSION >= 4
because the N-API versioning commit (8476053c) was not backported. So, the only option is to drop the guard.
Fixes: https://github.com/nodejs/node/issues/24249 PR-URL: https://github.com/nodejs/node/pull/25556
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
documentation is changed or added -
commit message follows commit guidelines