repl: simplify and improve completion

The completion lists used a hand crafted list of global entries that
was redundant due to also using the actual global properties for tab
completion. Those entries ended up in an separated completion group
which did not seem useful.

PR-URL: https://github.com/nodejs/node/pull/25731


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>