[NativeAOT] Switch to native arm64 msvc toolset

[jkotas]

We are always using x86/amd64-hosted msvc toolset when targeting arm64: https://github.com/dotnet/runtime/blob/main/src/coreclr/nativeaot/BuildIntegration/findvcvarsall.bat#L33-L34

This toolset runs under emulation when running on native Windows Arm64 machine.

Now that native arm64 hosted msvc is available (https://devblogs.microsoft.com/visualstudio/arm64-visual-studio/#for-native-developers), we should switch to defaulting to native arm64 msvc toolset when running on native Windows Arm64 machines.