Add support of dynamic switching between Graphics RHI backend APIs in runtime

Support dynamic switching of the Graphics RHI backends in runtime:
- On Windows switch between: DirectX, Vulkan.
- On MacOS switch between: Metal, Vulkan
- On Linux only Vulkan API is available.

RHI backend switching should be available both using command line flag and runtime hotkey.

Static linking with a single graphics API should be still supported as it is done now, for performance reasons.