Deploy pages from archives using archived tools

Rather than iterating over the available branches, checking them out
and building the pages, we are going to render the pages in a separate
jobs and pick up the artifacts created by those jobs. Tweak the
template `render-pages` in `.gitlab-ci/templates-render-pages.yml` to
retrieve and extract the artifacts rather than generating the pages.
Tweak the naming to be more consistent with its new role.

We need the tools to generate the main menu on every branch that
generates test-cases. Rather than copying the tools to them all, keep
the tools here, archive them and pull out the archive in the template
which is also stored on this branch.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>