test: rework to remove flakiness, and be parallel

Let .end() propogate from client, to server, and back, before
considering the test complete. Also, remove the test vector and exit
handling in favour of running all the tests in parallel and using
common.must/mustNotCall().

PR-URL: https://github.com/nodejs/node/pull/27300


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>