Adds feature for skipping include of doxygen headers into sphinx build
when env variable is set.
Builds incomplete docs (no function API documention)
but speeds up building (20min to 1<min).
Add this fast build as the default way of building docs in CI on
non protected branches.
- build_docs_pdf: now ignore docs related file patterns
- deploy_docs_preview: now ignore docs related file patterns
- .rules:build:docs: related jobs will not be triggered with `build` label
Also simplified the labels and ci
- Remove label regular_test, weekend_test
- Remove apply_job_filter
- check_submodule_sync: only run on protected branch