[!!!][TASK] Re-organize variable initialization for User Authentication

There are a lot of places where AbstractUserAuthentication
and the dependents (BE/FE user auth) set various settings,
both in the constructor and the start() method.

All possible settings are now moved to the constructor,
or to dependent properties in subclasses.

Some changes are now in place:
- UserAuth->loginType must be set now (which was previously
  in start()). This is now checked in the constructor.
- Most of the variables (sessionTimeout/sessionDateLifetime) are
  now set and evaluated inside the constructor, making start()
  much simpler to understand and read.

Resolves: #88527
Releases: master
Change-Id: Ie03b8b93f869f5bafae8f660d6c983bec308f2fa
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/60875


Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Georg Ringer <georg.ringer@gmail.com>