Simplify test matrix and remove merge queue

[konstin]

Currently, PR testing is a two-step process: First the regular PR tests, then the merge group tests. The test suite is flaky and test jobs take a long with limited parallelism, which means you can make a simple PR and 2h later get the notification that the PR failed due to an unrelated (and potentially temporary) error. There were several parts not passing when ran as a regular CI job. CI was failing a lot a blocking effective development. This PR radically simplifies the CI setup.

• Remove debian package: maturin is shipped with ubuntu 24.04
• Remove delete comments actions: github fixed this on their side
• Merge lint jobs and move to the test jobs: Remove the CI matrix a bit
• Only test minimum and maximum Python versions (3.9 to 1.13, 3.8 is EOL and 3.13 is out): Reduce the number of parallel jobs
• Deactivate jobs that only time out
• Remove cache-to from docker test: We don't need to cache every docker test build
• Remove the merge queue: Run all tests immediately. We don't have the volume that we would need merge groups
• Inline the test matrix: Without the merge queue, we don't need an extra job to compute the matrix or select jobs
• Build maturin (statically linked) in separate job and reuse the binary
• Fix dockerfile lints

By additionally changing the required jobs, we can switch to "merge when ready" so you don't need to return to a PR to check if CI is ready.