[FEATURE] Use utf8mb4 on mysql for new instances

If installing a new TYPO3 instance on mysql, utf8mb4 is now used as
default charset for the database connection and as default collation.

Upgraders may change LocalConfiguration to use utf8mb4, too. They
however need to take care of changing their collations and setting
according table detaults on their own.

A reports status check verifies there is no mixed collation.

Resolves: #80398
Resolves: #82080
Resolves: #82551
Releases: master
Change-Id: I6bf464a22c6ed74631bf5aacff9c2cfe670077da
Reviewed-on: https://review.typo3.org/56440


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Lienhart Woitok <lienhart.woitok@netlogix.de>
Tested-by: Lienhart Woitok <lienhart.woitok@netlogix.de>
Reviewed-by: Georg Großberger <garfieldius67@gmail.com>
Reviewed-by: Jigal van Hemert <jigal.van.hemert@typo3.org>
Tested-by: Jigal van Hemert <jigal.van.hemert@typo3.org>