FindVulkan: Add `dxc` (DirectX Shader Compiler) component

Adds DirectX Shader Compiler (HLSL to SPIR-V compiler) to the list of detected components in FindVulkan module. Not sure about dxc_lib and dxc_exe target names. dxc_lib test will most likely fail, considering how picky the library is about tinfo, although it works fine without it (when compiled from source).

Fixes: #23698 (closed)
Topic-rename: FindVulkan-dxc