[BUGFIX] Return all packages with PackageManager::getAvailablePackages

Currently the PackageManager loads installed package information by
default only. This patch adds a new flag to ensure all packages are
fetched before all available package information should be returned.

Resolves: #79078
Releases: master
Change-Id: I729c02f7b5c8303ee8d277aa88782274dff23591
Reviewed-on: https://review.typo3.org/51026


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>