Add autocomplete attribute to most password fields

What does this MR do and why?

Fixes #27125 (closed).

Add the appropriate 'new-password' or 'current-password' autocomplete attributes to the most common password fields. This ensures browser autocomplete and password managers understand whether the field is for current password or new password.

This should pretty well take care of the rest of #27125 (closed). I addressed a few other locations in !71237 (merged).

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