[FEATURE] Enable password view at the backend login

A user who's about to log in into the backend is now able to reveal the
typed password. Once the password field is cleared, the visibility mode
automatically switches back to its default to avoid revealing sensitive
data by accident.

Resolves: #86880
Releases: main
Change-Id: I3c45730e2bed9a71371e472729edf12c29bf5860
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/75380


Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Simon Schaufelberger <simonschaufi+typo3@gmail.com>
Tested-by: core-ci <typo3@b13.com>