Add pre-commit verification to CI

[maichmueller]

Builds on #1071.

Adds a CI step that verifies all pre-commit checks pass, otherwise fails the build step and exits. Not built on #1071 yet to keep diff small and the changes easily in sight. Will need #1071 merged into it to become operational.

Currently set as a condition for the build job to run, but can be set as a side job.

Merging this PR will mean that the entire codebase needs to apply the checks and formatting mandated by the pre-commit setup and as such requires one behemoth PR to apply these changes, otherwise all CI steps will constantly fail.

I do not recommend merging this until all open PRs in consideration for the project have been merged or closed so that the entire repo can see all of the pre-commit hooks applied to it.

[lanctot]

Hi @maichmueller, I think this is great, and in another world where I had enough time to properly look into it and understand how it all works, I would fully embrace the move. I realize it would probably save us time long term but I don't even have the time to spend on the initial cost of learning how it all works.

I also think this is a bit heavy for contributors and would rather keep doing what we have been and keep it easy to contribute.