Lint more YAML files in CI

Context

Closes #359968 (closed)

What does this MR do?

• We are extending the YAML linting to most YAML files in the repo (here is the current denylist).
• We are triggering the YAML job as soon as a YAML file got modified (more on that in the next section)
• We are only catching syntax errors for now.

Rationale

• The CI doesn't allow us (yet) to ignore files to trigger when using changes. We would need to do a whitelist, and it would be a big (brittle) one.
• The YAML job is fairly fast to run (at least locally)

To consider

• It might be too much to run the YAML job every time a YAML file for changed...
• Ideally, there would be a way to run the linting only on the files that got changed, but I could not find it.

How to set up and validate

remotely

I've created an MR to test out the changes in this branch. You can have a look at the pipelines for this MR:

• No changes in the YAML files: The YAML jobs aren't triggered
• A YAML error has been introduced (the same problem as in the original issue): The YAML job errors out
• The YAML problem is fixed, and another valid YAML change is introduced: the YAML jobs are triggered, and they are successful

locally

cd <your-local-gitlab-installation>

docker run -it \
  -e LINT_PATHS=".gitlab-ci.yml .gitlab/ci lib/gitlab/ci/templates data/deprecations data/removals data/whats_new" \
  -v $PWD:/code \
  registry.gitlab.com/pipeline-components/yamllint:latest sh

# Run default linting
yamllint --strict -f colored .

# Run pipeline linting
yamllint -d "{extends: default, rules: {line-length: disable, document-start: disable}}" $LINT_PATHS

echo $?