[!!!][FEATURE] Refactoring of FlashMessage rendering

This patch reverts some changes of #73698 and adds some new things:

- Introduce context based FlashMessageRenderer
- Add special FlashMessageViewHelper for the backend
- Cleanup classes related to FlashMessages
- Deprecate some methods from the FlashMessages::class

Resolves: #78477
Related: #73698
Releases: master
Change-Id: I937d5896b0a3d45e59c9174d233410f202add997
Reviewed-on: https://review.typo3.org/50285


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>