[BUGFIX] Followup Fluid Template Fallback paths

In the previously merged patch are some glitches and a regression:
- The usage (and test for existence) of deprecated functions has been
  removed.
- The value passed by the old behaviour is now considered last place
  in the array providing the lookup paths
- The typo preventing usage setLayoutPaths() has been removed.

Intended usage:
plugin.tx_a.view.templateRootPaths {
	default = <some default path>
	extendedA = <some additional path>
}
The array gets reversed and the first hit will be used as template.
In case only numeric indizes are used, the entries get ordered.
See unit tests for a more specific description.

Change-Id: If4fa75347614cf9b352c6016430a928833cc62cd
Resolves: #52971
Documentation: #52761
Releases: 6.2
Reviewed-on: https://review.typo3.org/24903
Reviewed-by: Alexander Stehlik
Tested-by: Alexander Stehlik
Reviewed-by: Marc Bastian Heinrichs
Tested-by: Marc Bastian Heinrichs