doc: initial cut at support tiers for diag tools

PR-URL: https://github.com/nodejs/node/pull/21870


Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Matheus Marchini <matheus@sthima.com>