gitlab: convert build/container jobs to .base_job_template

gitlab: convert build/container jobs to .base_job_template

This converts the main build and container jobs to use the
base job rules, defining the following new variables

 - QEMU_JOB_SKIPPED - jobs that are known to be currently
   broken and should not be run. Can still be manually
   launched if desired.

 - QEMU_JOB_AVOCADO - jobs that run the Avocado integration
   test harness.

 - QEMU_JOB_PUBLISH - jobs that publish content after the
   branch is merged upstream

As build-tools-and-docs runs on master we declare the requirement of
building amd64-debian-container optional as it should already exits
once we merge.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20220526110705.59952-5-berrange@redhat.com>
[AJB: fix upstream typo, mention optional container req]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20220527153603.887929-32-alex.bennee@linaro.org>