doc: improve assert documentation

1) Separate all loose and strict functions.
2) Stronger outline the used comparison rules in (not)deepStrictEqual
3) Fix SameValue comparison info

PR-URL: https://github.com/nodejs/node/pull/17002


Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>