worker: unify custom error creation

Mostly, this introduces a pattern that makes sure that if a custom
error is reported, `stopped_` will be set to `true` correctly in
every cast, which was previously missing for the
`NewContext().IsEmpty()` case (which led to a hard crash from the
`Worker` destructor).

This also leaves TODO comments for a few cases in which
`ERR_WORKER_OUT_OF_MEMORY` was not used in accordance with the
documentation for that error code (or according to its intention).
Fixing that is semver-major.

PR-URL: https://github.com/nodejs/node/pull/33084


Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>