Run benchmarks on merge queue, or manually

[jschneider-bensch]

This PR introduces merge_queue triggers for all jobs that are run on PRs and makes it so that benchmarks are only run on the merge_queue event, or when manually triggered.

[franziskuskiefer]

Generally lgtm, but the ML-KEM / benchmarks are still enabled. Let's move them to the merge queue as well.

Also, I enabled the merge queue. So we'll see if this works.

[jschneider-bensch]

Sorry, I missed that somehow.

Review re-requested

[franziskuskiefer]

Thanks.

I also moved everything over to the new rulesets. Let's see if that's working.