v8: implement v8.stopCoverage()

Add a v8.stopCoverage() API to stop the coverage collection
started by NODE_V8_COVERAGE - this would be useful in
conjunction with v8.takeCoverage() if the user don't want
to emit the coverage at the process exit but still want
to collect it on demand at some point.

PR-URL: https://github.com/nodejs/node/pull/33807


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>
Reviewed-By: Ben Coe <bencoe@gmail.com>