ARM64 support on macos-15 images

[duburcqa]

Images for macOS 15 has been released in the wild a few weeks ago (see github/roadmap#986, github/roadmap#987). Apparently now it features nested virtualisation, which should enable using docker in macOS VM. Although it is only a public beta at the time being, It would be nice to update this plugin so that it can leverage this capability on macOS-15 images.

[douglascamata]

@duburcqa they will only support nested virtualization if running on M3 and beyond, as stated in the docs: https://developer.apple.com/documentation/virtualization/vzgenericplatformconfiguration/4360553-isnestedvirtualizationsupported?changes=latest_minor.

I doubt Github already upgraded to M3 machines, but let's see.

[duburcqa]

Arf, I missed this information, you are right. I agree it is unlikely that they upgraded to M3 machines considering the little benefits of doing so overall apart from this specific capability. Feel free to close this issue if you want.

[duburcqa]

For the record, macos-15-xlarge is apparently running on M2 PRO chips (see github/roadmap#984). No M3 in sight and yet it is the best that Github has to offer.