[TASK] Streamline and optimize JavaScript in install tool

This patch optimize and streamline the JavaScript of Install.js
The following changes are part of the patch:

- Centralized FlashMessage handling
- Streamline server side and browser side severities
- Optimize performance, remove duplicate jQuery selector
- Remove console.debug calls
- Remove unused FlashMessage templates from views

Resolves: #78376
Releases: master, 7.6
Change-Id: I0652335e5d0bc4666896d5c7b6b528db445ee951
Reviewed-on: https://review.typo3.org/50553


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>