Moved tests from browsertests repository

See also the commit[1] that deletes the tests from browsertests
repository and the commit[2] in mediawiki/selenium repository that
documents changes in Jenkins jobs.

1: https://gerrit.wikimedia.org/r/#/c/112894/
2: https://gerrit.wikimedia.org/r/#/c/112899/
3: https://bugzilla.wikimedia.org/show_bug.cgi?id=49313#c2

Bug: 56419
Change-Id: Ifd6005bd1fd1a2ead6bd8c2d5194adafeed4b156