The descriptor heap implementation is a rather central behavior element
in vkd3d, so it's useful to have all the relevant information logged
in a single place.
Slightly simplifies descriptor write addressing, and makes layouts
essentially the same as array layouts, differing only in the binding
details, and therefore easier to understand. This also simplifies the
addition of storage buffer bindings, which can all be added onto the end.
Allows descriptor set layouts to be created after all bindings are
mapped. This is less complex and fragile than the current scheme, and in
a future patch it will support separating descriptor types into different
sets. Descriptors on virtual heaps are currently allocated from pools
which contain an equal number of each descriptor type used by vkd3d, and
this can waste a significant amount of device memory.
Enables the bounded range to be mapped to the unbounded one, instead of
being mapped to a separate binding which will be populated from the same
d3d12 descriptors as the unbounded one.
Based on the design document, "The runtime will not clamp or validate
the input, but implementations may clamp to the range [0,1] if necessary.",
so we test for the EXT_depth_range_unrestricted extension, and only clamp if
it's not available (thus, necessary to do so).
NaNs are converted to zero as per "NaNs must be treated as 0, but the runtime
will convert NaNs to 0 on behalf of the implementation.", and a default bounds
are set to 0.0 and 1.0.
The existing code sets "stageFlags" to VK_SHADER_STAGE_ALL when
"use_vk_heaps" is true, but doesn't adjust the visibility. This
potentially violates the "Any two elements of pPushConstantRanges must
not include the same stage in stageFlags" constraint, and causes the
validation layers to complain accordingly.
