[BUGFIX] Fix accessibility issues of system news

The system news slider implements the ARIA pattern "carousel"
except for the omission of aria-roledescription which has
no support in current screen readers.

Additionally the contrast of the slider controls has been
increased and the click size does not shrink on small screens.

Resolves: #93259
Releases: master
Change-Id: Ia718184f9b4188c57c08d63f34bb05d80be37ced
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67456


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Richard Haeser <richard@richardhaeser.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Richard Haeser <richard@richardhaeser.com>