build: switch vulkan validation/utility libs to conan-center recipes

Conan Center now ships vulkan-validationlayers and vulkan-utility-libraries,
so drop the in-repo recipes and bump the whole Vulkan stack from 1.4.313.0 to
1.4.350.0 (the version Conan Center provides for these two).

The official vulkan-validationlayers package has an empty cpp_info (runtime
layer only), so the CMakeConfigDeps generator declares no usable target.
Recreate the imported target in Registry.cmake so it can still carry the
RUNTIME_DEP layer files and be linked by RHI-Vulkan, and locate the layer
dll/json via vulkan-validationlayers_PACKAGE_FOLDER_RELEASE instead of the
now-empty include dir.

Author: FlyAndNotDown