[!!!][TASK] Always render frontend in UTF-8

This removes the option config.metaCharset and the
conversion of content everywhere.

The public method "TSFE->convOutputCharset" is gone.
The property "config.metaCharset" has no effect anymore.

Resolves: #97065
Releases: main
Change-Id: I657b68adeba3501612ae0959fe54bdeb6470305c
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/73698


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Susanne Moog <look@susi.dev>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Susanne Moog <look@susi.dev>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Benni Mack <benni@typo3.org>