mediawiki.special.block: Add hide user option
Hide user option should show under additional options when a user has the 'hideuser' right. Currently this option is not enabling/disabling till the expiration field is added in T359684
Bug: T361148
Follow-up: I1e77a63133b8c8ea043c680ddb8af0e044a6fb31
Change-Id: I1dde527575324e5345e6368d9ca8338b713959ad