Pipeline · cubicweb / RQL

ci: Update CI config to use predefined templates

- Use gitlab ci templates include
- Fix various F811 errors, redefinition of unused ...
- Remove now useless triggered jobs: `trigger-cubicweb-pipeline` & `trigger-readthedocs`

6 jobs for !51 with topic/default/ci-experiment in 1 minute and 23 seconds (queued for 2 seconds)

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