MNT: Remove explicit password arguments from methods

We recently noticed (e.g. see discussion here: https://github.com/astropy/astroquery/pull/2386#discussion_r863120399) that there is some usage of explicit password arguments in the user facing API for several modules. We should clean up all of these and instead use keyring, prompting for password, environ variables, etc.
I don't have a concrete recipe we have to follow, please feel free to use this issue for discussions. The aim would be to do something very similar over all our modules. Once we reach an ideal solution, we should document it, too either in the template or narrative docs.

The testing part of this question is most certainly not solved as that issue has been raised in #2367 already.

I'm pinging the authors/maintainers of the relevant modules.

cc @esdc-esac-esa-int, @andamian, @keflavich, @olyoberdorf

Start with the discussion in pull request #2386 and audit the user-facing APIs across the relevant modules for explicit password arguments. The issue leaves the replacement strategy open, so compare keyring, prompting, and environment-variable approaches before proposing a consistent direction. Done means password arguments are removed across the modules and the chosen credential handling is documented; testing is separately tracked in #2367.

Written by the indexing model from the issue text.