[BUGFIX] Respect automaticInstallation setting in extension manager

Prevent the automatic installation of new extensions if the setting
was disabled.

Resolves: #84125
Releases: master, 8.7, 7.6
Change-Id: Ic554e8870543b2f15079f7adfb1ddc2517bfc2b5
Reviewed-on: https://review.typo3.org/56361


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>