CI: Swap to MacOS 14 runner

[stenzek]

Description of Changes

GitHub recently enabled M1 runners for public projects. They bring a considerable speed boost to CI runtimes, DuckStation went from 15mins+ down to 3mins after switching.

Can't use MoltenVK from brew anymore, because that's going to be arm64. So, build it ourselves as part of the deps package. It doesn't take long on M1 :-).

Only caveat is now we're building on ARM, so we have to be careful and make sure we actually create an x86 build. Luckily I'd already done most of this so I could run the x86 build script on my Macbook.

Rationale behind Changes

Vroom vroom.

Suggested Testing Steps

Test Mac builds ~~, once I actually get it working. I have a feeling it's going to explode at first~~ .