Support Apple Silicon ARM64 architecture natively

[michelleangela]

VS Code now works on Apple Silicon (microsoft/vscode#101662).

This is a feature request to enable the language server binaries to also run on Apple Silicon natively.

The feature request to have the debugger binaries run on Apple Silicon natively is tracked by #7035.

Note: the cpptools, cpptools-srv, and debugger binaries built for macOS x64 may work on Apple Silicon's x64 emulator, however this may use more resources than having binaries run natively as ARM64 on Apple Silicon.

[sean-mcmanus]

I think we'll need Azure support for Big Sur first: actions/runner-images#2072 ... unless we can get a "hosted" Big Sur machine added (I don't see one currently).