Review GitHub actions

[colisee]

Changes

• Drop arm32 build
• Parallelize amd64 and arm64 builds
• Rename some repository variables for consistency
• Drop scheduling trigger for releases (they are built only once)
• Bump default php version to 8.5.7

[colisee]

Build time decreased from 30 minutes to 5 minutes.

[ikke-t]

lgtm

[ikke-t]

Wau, quite an improvement.

[JohnVillalovos]

@colisee Since I hate merge commits I rebased it...

[JohnVillalovos]

@colisee LGTM.

I just had one question on why the schedule was removed. But I still approve.

Thanks.

[JohnVillalovos]

Why is the schedule being removed?

[colisee]

@colisee LGTM.

I just had one question on why the schedule was removed. But I still approve.

Thanks.

I decided to remove the schedule for release images because we could end up with different images (caused by apt-get update && apt-get upgrade) while bearing the same image tag.