kubernetes: Use separate image repo for single version image build

config.py:

Replace mediawiki_image_name, mediawiki_debug_image_name, and
mediawiki_cli_image_name with mediawiki_mv_image_basename and
mediawiki_sv_image_basename.

mediawiki_mv_image_basename is restricted/mediawiki-multiversion and
mediawiki_sv_image_basename is restricted/mediawiki-singleversion.

kubernetes.py:
Use mediawiki_sv_image_basename when building the next image, otherwise use
mediawiki_mv_image_basename.

Construct the remaining image names by appending -debug and -cli
to the basename.

Bug: T398875