v3dv/descriptor_set: support for array of ubo/ssbo

v3dv/descriptor_set: support for array of ubo/ssbo

For that we include the array_index when asking for a ubo/ssbo index
from the descriptor_map.

Until now, array_index was not included, but the descriptor_map took
into account the array_size. This had the advantage that you only need
a entry on the descriptor map, and the index was properly return.

But this make it complex to get back the set, binding and array_index
back from the ubo/ssbo binding. So it was more easy to just add
array_index. Somehow now the "key" on the descriptor map is the
combination of (set, binding, array_index).

Note that this also make sense as the vulkan api identifies each array
index as a descriptor, so for example, from spec,
VkDescriptorSetLayoutBinding:descriptorCount

 "descriptorCount is the number of descriptors contained in the
  binding, accessed in a shader as an array"

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6766>