Add support for Apple Intelligence

[tjweir]

Add On-device Apple Intelligence as a provider.

[64bit]

Hey good idea!

I dont see the actual provider implementation?

Also this should not be behind feature gate because the cli can be installed using brew. But yes macos and arch64 in compilation cfg make sense.

For example see litert-lm implementation, where if required dependency is not installed it prompts user to visit link to doc hosted by Google - so we dont need to document - the cli guides user.

Do you mind making these changes and requesting a review?

[tjweir]

Lulz, may be a good idea for me to add the files!

Apple Intelligence is at a system level. I suppose I could tell people what they need to do to enable it.

[64bit]

Love it, thank you for adding Apple Intelligence support!