Define a downstream job that takes a WMF MediaWiki version as a
parameter and builds/publishes a production image containing only that
version.

Parameterized and renamed the upstream job to better reflect its general
utility as a job that can cut a new WMF version branch and publish an
image for it. Note that the existing job with the old name may have to
be removed manually upon deployment.

Bug: T369115
Change-Id: I78b2c23e3d024a657463cc08c056b60126be2d08