[TASK] Make code of EXT:dashboard consistent with other system extensions

Made sure EXT:dashboard follows the guidelines for usage of ext_localconf
and ext_tables and some other changed to make the code more consistent
with other system extensions.

Resolves: #91108
Releases: master
Change-Id: I82d957a9e13aee8504b6bf8df6a3145b8fb6a5db
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64221


Tested-by: Christian Eßl <indy.essl@gmail.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Richard Haeser <richard@maxserv.com>
Reviewed-by: Christian Eßl <indy.essl@gmail.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Richard Haeser <richard@maxserv.com>