[FEATURE] Basic TypoScript syntax scanner

This patch adds a last feature to the PageTsConfig and
TypoScript UI in TYPO3 v12. A simple syntax scanner:
* Detect missing and excess braces
* Detect invalid lines - for instance "foo <" which
  missses an identifier stream on the right side.

This is a basic set, the main visitor can be extended
later to look for additional details, for instance
looking for @import lines that can't find any includes.

The patch introduces the main logic. Note the "source"
display is a bit fiddly currently, it mirrors some
issues from the existing "source" display of included
nodes: This area should receive fine additional fine
tuning patches.

Apart from that, the patch finally brings a ReST file
about the new / refactored PageTsConfig and TypoScript
modules.

Change-Id: Id1e6fdcbc294c6f8c3be0520e7e0ae1d50287b16
Resolves: #100218
Related: #97816
Releases: main
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/77364


Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>