Moved most of TextExtracts.php to the new extension.json
and added method for backward compatable implementation
of the extension if still called though the php file. Moved
unit test hook to Hooks.php and deleted old il8n.php.
Bug: T87979
Change-Id: I3d26bd931ad2941268b94474f3e6327282da24ec
Change I7b37295e for mediawiki/core deprecates several methods, and more
importantly changes the format of the data returned from
ApiResult::getData(). This change should handle these differences in a
backwards-compatible manner.
Change-Id: I7b37295e8862b188d1f3b0cd07f66ac34629678e
