[BUGFIX] Use RequestFactory for downloading mirrors and check response properly

The LanguagePackService now uses the RequestFactory to download the
mirrors.xml.gz file, since it throws proper exceptions on failures.

In case of e.g. a timeout, the thrown exception is properly caught and
the designed fallback kicks in.

Resolves: #89810
Releases: master, 9.5
Change-Id: Ie4e8bcf02c33eb18e58f505f1a791c1233d6f593
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/62496


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Richard Haeser <richard@maxserv.com>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Richard Haeser <richard@maxserv.com>