Determine whether we can drop MTLGPUFamilyMac1 support #5187

MTLGPUFamilyMac1 is deprecated since macOS 13 and iOS 16.

Dropping support came up in #5179 - @mwyrzykowski:

We could also make it part of core and drop Mac1 family down to compat. I think the last Intel Mac to support Mac1 was Intel Skylake from 2015, but perhaps there are eGPUs which are Mac1 as well?

There are probably a few other things we could support in core if we did this.