[TASK] Protect methods in AbstractLinkBrowserController

Some public -> protected changes for AbstractLinkBrowserController
and BrowseLinksController

Resolves: #86193
Releases: master
Change-Id: I349dd5961ac2d90ede36a17c4d4ca550171e315e
Reviewed-on: https://review.typo3.org/58223


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Andreas Wolf <andreas.wolf@typo3.org>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>