`checker.yml` and `integration.yml` are the only workflows that are currently safe to be executed simultaneously, the others present a risk that the order of completion may not be expected. The ones that are chained from `integration.yml` can be called as many times as `integration.yml` workflows are running at that moment, the same with the trigger "workflow_dispatch".
This can be fatal for workflows like `container.yml` that use a centralized cache to store and load the candidate images in a common tag called "searxng-<arch>".
* For example, a `container.yml` workflow is executed after being chained from `integration.yml` (called "~1"), and seconds later it may be triggered again because another PR merged some breaking changes (called "~2"). While "~1" has already passed the test job successfully and is about to start the release job, "~2" finishes building the container and overwrites the references on the common tag. When "~1" in the release job loads the images using the common tag, it will load the container of "~2" instead of "~1" having skipped the whole test job process.
The example is only set for the container workflow, but the other workflows might occur in a similar way.
Instead of executing the workflow after integration.yml completes correctly, let's run this workflow parallel to integration.yml restoring the original behaviour.
documentation.yml will run after integration.yml COMPLETES successfully (will
defer anything depending on integration.yml until heavy loads like container
building are moved to separate workflows) and in master branch.
Style changes, cleanup and improved integration with CI by leveraging the use of
shared cache between all workflows (not functional until all workflows have been
refactored).
