Run tests for ARM64

There are several prerequisites needed to run the ARM64 tests.

* ARM64 [Dpdsv6](https://learn.microsoft.com/en-us/azure/virtual-machines/sizes/general-purpose/dpdsv6-series) (Cobalt 100) is now available on Azure.
* ARM64-native MSVC is now available.
* [ARM64-native Python](https://www.python.org/downloads/windows/) is now available.
* Clang/LLVM can now target ARM64 on Windows.