Refactor .gitlab-ci.yml using templates

.gitlab-ci.yml is getting too complex, having several branches for compilations with xrootd-4 or 5 and tests using EOS-4 or 5. And in the near future support for other linux distributions as Centos Stream 8.

It would be necessary to use templates and to include them.

This issue will close this issue related to show the CI Variables https://gitlab.cern.ch/cta/CTA/-/issues/1193

Related: https://gitlab.cern.ch/cta/CTA/-/issues/1230 and https://gitlab.cern.ch/cta/CTA/-/issues/1193

Links: extends job_control yaml_optimization parallel-matrix-jobs