[TASK] Apply current recommendations for BASH scripts

This patch applies the current recommendations for BASH scripts see
https://github.com/koalaman/shellcheck#readme.

Resolves: #95964
Releases: master, 10.4
Change-Id: I21ba18cb151acc0ff8f33a2135ef289669d15bab
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71981


Tested-by: core-ci <typo3@b13.com>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>