Build CK on Windows

[vpietila-amd]

Proposed changes

Enable building CK on Windows. The Windows build assumes that TheRock is installed to the standard location. Main changes:

• In the main CMakeLists.txt, I enabled HIP language only after the HIP package found. Otherwise the configuration step fails on Windows. The master CMakeLists.txt has some Windows platform specific changes for finding the ROCm installation because the paths are slightly different on Windows.
• For CK tile, fixed type casting issue for min and max utility functions that the MSVC compiler complains about. Only impacts Windows platform.
• For both CK and CK Tile, suppressed getenv deprecation warning on Windows platform in the env var utilities.
• For CK Tile joinable_thread, created a no-op implementation on Windows platform. No functional change on Linux platform.
• Updated Readme with the Windows build instructions.
• Added a Powershell script for running tests on Windows platform. The same script can be used on Linux platform if .NET Core is installed.