Split CI builds into workflows for each OS

[aaronfranke]

Implements this proposal on IRC:

[11:51:51] <Akien> RevoluPowered: So, GitHub Actions has this huge flaw: https://github.community/t/ability-to-rerun-just-a-single-job-in-a-workflow/17234/16
[11:52:00] <Akien> If one job fails, you have to re-run *all* jobs.
[11:52:35] <Akien> But it seems we could work it around by splitting each job in its own workflow, as it seems "Re-run all jobs" only re-runs all jobs in the current workflow (so currently it doesn't re-run static checks for example)
[11:58:45] <Akien> We can likely split by platform at least (so we for desktop we still have two jobs per workflow)

I also changed the workflow names, since "Godot" seemed redundant. Not sure what to do about "Static Checks / Static Checks".

The main annoying thing is that the builds aren't in order by their name. It seems that they are ordered based on which jobs are the first to be executed.

[akien-mga]

Needs a rebase to fix the javascript CI as it broke overnight.

[akien-mga]

The main annoying thing is that the builds aren't in order by their name. It seems that they are ordered based on which jobs are the first to be executed.

Yeah that's a bit annoying but I'm not sure we can solve that. I guess it's not too bad, what's most important is to be able to find the builds that failed (red cross).

[akien-mga]

CC @RevoluPowered

[akien-mga]

Thanks!