assert: improve assert.fail() API

assert.fail() has two possible function signatures, both of which are
not intuitive. It virtually guarantees that people who try to use
assert.fail() without carefully reading the docs will end up using it
incorrectly.

This change maintains backwards compatibility with the two valid uses
(arguments 1 2 and 4 supplied but argument 3 falsy, and argument 3
supplied but arguments 1 2 and 4 all falsy) but also adds the far more
intuitive first-argument-only and first-two-arguments-only
possibilities.

assert.fail('boom');
// AssertionError: boom

assert.fail('a', 'b');
// AssertionError: 'a' != 'b'

PR-URL: https://github.com/nodejs/node/pull/12293


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>