Issue #3636782: Resolve phpstan issues in metatag_views, GroupBase,...

Resolves the PHPStan errors listed in the issue: removes the natively typed $entityTypeManager redeclaration in MetatagViewsTranslationController, replaces deprecated Request::get() with attributes->get() in the Views forms, injects the cache factory into MetatagViewsCacheWrapper instead of the undefined $this->container, guards the deprecated cacheExpire() call with DeprecationHelper, fixes the inline @var and the GroupBase @return docblocks. Also fixes the MetatagManager empty() check and the deprecated getDrupalRoot() call in V2UpdatesTest reported by CI.

Related to #3636782