gitlab: introduce a common base job template

gitlab: introduce a common base job template

Currently job rules are spread across the various templates
and jobs, making it hard to understand exactly what runs in
what scenario. This leads to inconsistency in the rules and
increased maint burden.

The intent is that we introduce a common '.base_job_template'
which will have a general purpose 'rules:' block. No other
template or job should define 'rules:', but instead they must
rely on the inherited rules. To allow behaviour to be tweaked,
rules will be influenced by a number of variables with the
naming scheme 'QEMU_JOB_nnnn'.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20220526110705.59952-2-berrange@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20220527153603.887929-29-alex.bennee@linaro.org>