[TASK] Replace Bootstrap::initializeLanguageObject() in tests

This change uses the LanguageServiceFactory
directly (mostly in tests) instead of
Bootstrap::initializeLanguageObject() in order
to explicitly define $GLOBALS['LANG'], thus showing
the dependency to the global object.

The internal method Bootstrap::initializeLanguageObject()
can thus be removed.

Resolves: #102712
Releases: main
Change-Id: I78a93e222d302db796a031e585685a409aa73c41
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/82266


Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Nikita Hovratov <nikita.h@live.de>
Tested-by: Oliver Klee <typo3-coding@oliverklee.de>
Tested-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: Nikita Hovratov <nikita.h@live.de>
Reviewed-by: Stefan Bürk <stefan@buerk.tech>
Tested-by: core-ci <typo3@b13.com>