Remove Utils::lookup[User]MultilangText() and related functions

Replaced by language fallback chain.

Utils::languageChain(), which has no usage in Wikibase, is removed too.

Other removed functions include those lookup* functions' dependency,
Utils::filterMultilangText() and Utils::reorderArray().

Change-Id: I40ad9647ba489a7950773f21a2ec04273ef1fe9e
Merge "Remove Utils::lookup[User]MultilangText() and related functions"