assert: improve error messages

From now on all error messages produced by `assert` in strict mode
will produce a error diff.

Backport-PR-URL: https://github.com/nodejs/node/pull/19230
PR-URL: https://github.com/nodejs/node/pull/17615


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>