Move nightly to workflow_call

[iluuu1994]

This PR removes most of the logic of nightly_matrix.php by converting nightly.yml to a workflow_call, and invoking it multiple times for each branch in a new root.yml workflow. The naming of the files is intentionally kept to make the diff readable. They may still be renamed afterward.

A test run is here. I'll check tomorrow whether it actually works. 🙂
Edit: Another one

• Coverage and Pecl should only run on master
• libmysql produces a compile error on 8.1
• Observer tests are missing the zend_test.observer.show_output=1 ini setting on 8.1

All errors, except for the community build that also occurs in the current nightly should be fixed. I will look at that soon.

[cmb69]

Thank you very much! This looks like a very nice improvement; especially the job overview (on the left) is now readable. I assume that this also supersedes #16144.

[TimWolla]

Didn't look at all the changes in detail, but the results are clearly much better. Thanks!

[iluuu1994]

I assume that this also supersedes #16144.

I forgot about this one. I think that PR still makes sense.