[FEATURE] Debug register and page with TypoScript

Adds the possibility to show the content of
$GLOBALS['TSFE']->register and $GLOBALS['TSFE']->page
with the debug option in getText.

Example:
10 = TEXT
10.data = debug:register
20 = TEXT
20.data = debug:page

Resolves: #49478
Releases: 6.2
Change-Id: I79b118fd2450193a6573569f7ec99b8159f973bc
Reviewed-on: https://review.typo3.org/21695
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind