FindVulkan: Add support for cross-compiling between Windows x64/ARM64

The LunarG Vulkan SDK on Windows provides arch-specific library
directories for cross-compiling.  On X64 hosts it provides `-ARM64`
directories.  On ARM64 hosts it provides `-X64` directories.

It also provides arch-specific `bin` directories, but only for the
`.dll`s of the cross architecture.  We still want the plain `bin`
directory containing host-architecture executable tools.

Co-authored-by: Giancane, Francesco <fgiancan@qti.qualcomm.com>
Co-authored-by: Arnaud, Adrien <aarnaud@qti.qualcomm.com>
Tested-by: Giancane, Francesco <fgiancan@qti.qualcomm.com>
Tested-by: Arnaud, Adrien <aarnaud@qti.qualcomm.com>