Improve handling of the format of the VRS image

[RandomShaper]

• Validate format conservatively. (This is to have VRS images created regardless whether VRS attachments are supported, which avoids errors in places where the code assumes such images were created on low-spec GPUs.)
• Create a non-layered default VRS image, which is what Vulkan (and D3D12, by the way) expect.

Fixes #63578.

[akien-mga]

Thanks!

[BastiaanOlij]

@RandomShaper under Vulkan VRS images can be layered when Multiview is used. Strange though that it would error out when a single layer texture is supplied.. Anyway, should be a safe change.

[RandomShaper]

I realize I should have worded it better. The error from Vulkan is about certain shader having the former 2D one-element texture array bound to a non-array texture uniform. The piece about D3D expecting a single layer for VRS is true, but doesn't really have a point here. I mixed concepts up while writing the description.