test: refactor assert test

This adds puctiations to the comments, uses a capital letters for
the first character, removes a few obsolete comments and switches
to assert.ok when suitable.

It also moves all `assert.deepEqual()` and `assert.deepStrictEqual()`
tests to the appropriate file.

PR-URL: https://github.com/nodejs/node/pull/18610


Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>