Previously, we have had four iOS RIDs:

iOS-arm
iOS-arm64
iOS-x86
iOS-x64

Apple has never shipped an iOS device with an x86 or x64 processor. Instead, the x86/x64 RIDs have meant "iOS simulator with these arches" as opposed to "iOS with these arches". Amongst other things, that means building against a DIFFERENT SDK, iPhoneSimulator.platform vs iPhoneOS.platform

In the Apple Silicon future, the iOS simulator is now an ARM64 binary - so we need:

iOS-arm
iOS-arm64
iOS-arm64, but built against the simulator SDK not the device SDK
iOS-x86
iOS-x64
Clearly, there's a problem.

The solution is to move the simulators to a different RID, to avoid the overloading issue:

iOS-arm
iOS-arm64
iOSSimulator-arm64
iOSSimulator-x86
iOSSimulator-x64

This PR introduces the new entries in the RID graph, moves our existing iOS-x{86,64} to iOS-sim-x{86,64}, adds a new iOS-arm64.

The above also applies for tvOS, with a smaller set of OSes:

tvOS-arm64
tvOSSimulator-arm64
tvOSSimulator-x64

Ref: #48216