Outdated manuals which are not supported anymore are removed.
The missing system extensions manuals are added.

Some special cases:
- t3install was renamed to t3upgrade (as the Installation Guide
  was also renamed to Upgrade Guide)
- t3l10n and t3translate are duplicates, t3l10n was removed

The current list of manuals is maintained in
https://github.com/TYPO3-Documentation/TYPO3CMS-Example-ExtensionManual

Resolves: #102035
Releases: main, 12.4
Change-Id: I344f8a17d1c5de9dbcdc5148bed5322518d72b0c
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/81218


Tested-by: Lina Wolf <112@linawolf.de>
Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Lina Wolf <112@linawolf.de>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>