[BUGFIX] Element file browser respects allowedExtensions

The type=input, renderType=inputLink field control has an option
"allowedExtensions" to restrict the file element browser to specific
file endings. This option is now correctly considered in file browser.

Change-Id: Ic42bd0de06002f308d7db4098c704ca2574e4018
Resolves: #82861
Releases: master, 8.7
Reviewed-on: https://review.typo3.org/54520


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