Windows ARM64: Automatically select the correct `targetArchitecture` for attach

## Environment

* OS: Windows ARM64
* ARM64 .NET SDK installed
* x64 .NET Runtime installed

## Steps to reproduce

1. Create a new console app (`dotnet new console`)
2. Open the folder in VS Code and generate assets for build and debug
3. Add a `Console.ReadLine()` (or anything else to keep the app from immediately exiting)
4. Open a command prompt and run the app using the x64 dotnet.exe to run the dll as an x64 process instead of an ARM64
5. Attempt to attach

## Expected behavior
Attach should succeed

## Actual behavior
Attach fails with `Unable to start debugging. Failed to attach to process: The .NET debugger can only debug x64 processes.`

## Work around
Modify launch.json to add `"targetArchitecture": "x86_64"`