util: improve `inspect()` compact number mode

This fixes a proportion calculation for lots of short array entries
with at least one bigger one that alone makes up for more than one
fifth of all other entries together.

PR-URL: https://github.com/nodejs/node/pull/26984


Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>