dzn: Take VK_IMAGE_CREATE_MUTABLE_FORMAT_BIT into account

dzn: Take VK_IMAGE_CREATE_MUTABLE_FORMAT_BIT into account

Use a typeless format when VK_IMAGE_CREATE_MUTABLE_FORMAT_BIT is
set, so we can cast to compatible types at least. Still doesn't
work when formats are of the same size but from incompatible
types (like R32_FLOAT and RGBA8_UNORM), which Vulkan considers
as compatible while D3D12 doesn't, but it gets us closer to what
the Vulkan API wants.

D3D12_FEATURE_DATA_D3D12_OPTIONS12::RelaxedFormatCastingSupported
should address the remaining limitations.

Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17368>