Recovering Allen CI pipeline

• move ecal decoding and electron lines in non-default sequence (!675 (merged))
• temporarily disabling hlt1_pp_no_gec tests (!665 (merged)), remove Jenkins tests (in Moore?) and tests related to hlt1_pp_no_gec (MooreAnalysis!53 (merged))
• move to merge request pipelines (https://docs.gitlab.com/ee/ci/yaml/index.html#workflowrules-templates)
• Specify tag docker-privileged-xl in build runners (https://cern.service-now.com/service-portal/?id=kb_article&n=KB0005851) (!676 (merged))

!508 (closed) can solve the problem at long term