Move CI from GitHub Actions to GitLab (#814)

* CI: do not trust this CI 1

* CI: don't want to trigger unneded statuses

* CI: debug 1

* CI: new CI

* CI: temp allow failure

* CI: exclude paths

* doc: check if docs won't trigger pipelines

* doc: check hybrid changes pipeline

* doc: do not push excluded files together with others

* CI: undebug fmt

* CI: better deny

* CI: fix deny and spellcheck

* CI: global backtrace

* CI: deny config

* CI: publishing

* Dockerfile: metadata fix [skip ci]

* CI: revert me

* CI: debug bash

* CI: mv ci.Dockerfile; fix buildah bug

* CI: fix artifact name

* Dockerfile: fix context

* CI: separate deny check licenses

* CI: when to run

* CI: unneded stuff in these Dockerfiles

* CI: merged test-refs and build-refs

* CI: test-build optimizations

* CI: changes, web, scheduled pipelines now work as intended

* CI: use tested production CI image

* CI: substitute GHA

* Fix clippy.

* Moar clippy fixes.

* Fix more.

* Finally fix all?

Co-authored-by: Tomasz Drwięga <tomasz@parity.io>