Refactor CI checks in `ci.yml`

[tpvasconcelos]

Motivation: CI checks take too long to finish

TODO:

• Adapt pre-commit invocation in tox -e pre-commit to run only against staged files
• Disable pre-commit in ci.yml: I've recently installed the pre-commit.ci GitHub App so we no longer need to run pre-commit as part of the tox -m static checks
• Add on.pull_request.paths: and on.push.paths: filters to ci.yml to only trigger the checks when python files have changed (e.g. cicd_utils, tests, src etc...) This is most definitely not a good idea! Maybe we can add some paths-ignore: entries instead in the future.