[TASK] Make TS content templates more flexible

If an extension used static content ID 43 (content default),
it also added itself (during each runtime of ext_localconf.php)
to all available content blocks.
The original way is problematic as an extension that
provides content templates may be included after
an extension that wants to add itself after all content
templates.
This is now more confusing as the package manager
resolves the ordering of extensions and now,
CSS Styled Content gets loaded after felogin and
indexed_search.

To resolve this problem completely, the additional
TypoScript for each "contentRenderingTemplate",
a TS template that provides default content renderings,
is added to one global default TypoScript and is only
merged at the TemplateService class.

Therefore the extension loading ordering does not
matter anymore.

Resolves: #55942
Resolves: #55174
Resolves: #55557
Releases: 6.2
Change-Id: Id0c983bf96a3a76fde2183c57a17066ef8fd4ac8
Reviewed-on: https://review.typo3.org/27587
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind