[FOLLOWUP][BUGFIX] Prevent out of bounds exception in password generation

This followup prevents an out of bounds exception and
adds a couple of tests for the new functionality.

The min length is now set to 8. This is now also checked
when using the special "random" option.

Resolves: #98540
Releases: main
Change-Id: I5e89813794a0178b7d9c835e89c6272128b4b8c3
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/76461


Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Oliver Bartsch <bo@cedev.de>