Speed up builds
Hi simjanos, long time no see!
This PR is made to address the slow build times for ARM64 and to fix the various warning in the CI.
On my testing, the first build was done in the amount of time you are used to, 20 minutes for PHP ARM64 image, but the second build used the cached layers and was done in just 2 minutes 40 seconds.
I have not reinstated the Python ARM64, that's up to you for when you decide to enable back. Feel free to test it, and if it is good then we might want to reproduce these changes for the dev and release actions too.
I have also noticed you have been using pre-releases to signal that a beta was out, please let me know if you want me to change this action from manual to be triggered on a pre-release instead.
Cheers.