test: split test-embedding.js and run tests in parallel
Split the tests so that it's easier to isolate and debug issues,
and we can run the test cases in parallel to speed up. Also
add more comments about what they are testing.
PR-URL: https://github.com/nodejs/node/pull/61571
Backport-PR-URL: https://github.com/nodejs/node/pull/65219
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
