test: add test case for completion bash flag

This test case verifies that starting Node.js with the completion
bash flag prints out the expected result and ends right after.

PR-URL: https://github.com/nodejs/node/pull/24168


Reviewed-By: Bryan English <bryan@bryanenglish.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>