util: avoid out-of-bounds arguments index access

This updates util.inspect() to avoid accessing out-of-range indices of
the `arguments` object, which is known to cause optimization bailout.

Based on an average of 10 runs of the benchmark in
`benchmark/util/inspect.js`, this change improves the performance of
`util.inspect` by about 10%.

Relates to https://github.com/nodejs/node/issues/10323

PR-URL: https://github.com/nodejs/node/pull/10569


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Jackson Tian <shyvo1987@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>