ci: shard the test run on mac os X This should comes with some benefit: - spread the load across more runner, - reduce the real-time CI run, - reduce the "retry" run when we need them. We start with the Mac jobs, but that would be tremendously useful for Windows too. For linux, we need to reduce the startup overhead for this to be worth it. Building smaller image and speeding up clone should help with that.

run-tests: implement crude sharding support It will help to spread the testing load across more CI runners.

ci: have the mac test run if you trigger building the mac wheel The mac test job now depends on the wheel building. And the wheel building is manual. So if the mac test job is set to "on_success" if will be "skipped" by default, and automatically run if the wheel are build. That is especially handy as we are about to shard that test and that the UI for manual sharded test sucks.

ci: adjust the starting port range to runner concurrency If multiple job runs on the same runner, they should not use the port range.

ci: move the "tempory work dir" to "concurrency-safe" location Lets not use a global location and move at the root of the directory dedicated to the job.

ci: abstract the of absolute /tmp/ path We now have a TMP_WORK_DIR directory that we can update to a more sensible value in the next changesets.

ci: rationalize variable usage The usage of "extends" allow to skip a lot of duplication. We also introduce more fine grained variables to help finer override.

ci: move some variables closer to their usage These were defined globaly because we had trouble making them inherited. This is now fixed, so we can get them were they belong.

ci: use extends instead of <<: *x The old form is a yaml construct that make it hard to share variable definition. The "extends:" key is a gitlab specific that preserve the variable definition and just add the new ones. This will help us to reduce duplication. This has the effect of fixing some of variants definition we though we set while we did actually not. Most notably, the "rust" variant for 3.12 and 3.13 seems fully broken in the CI (possibly because some rust-cpython version issue?). This changeset only reveal such breackage and does not introduce them.

ci: use the macos wheel to run tests

wheel: build mac os wheel through the CI Let's start building wheel for mac os X too.

pycompat: drop some now useless workaround for makedirs This `exists_ok` flag was added in Python 3.2