Its value on input is ignored. QFV_CreateResource writes the resource
object's offset relative to the beginning of the shared memory block.
Needed for the Draw overhaul.
This moves the qfv_resobj_t image initialization code from the IQM
loader into the resource management code. This will allow me to reuse
the code for setting up glyph data. As a bonus, it cleans up the IQM
code nicely.
The resource subsystem creates buffers, images, buffer views and image
views in a single batch operation, using a single memory object to back
all the buffers and images. I had been doing this by hand for a while,
but got tired of jumping through all those vulkan hoops. While it's
still a little tedious to set up the arrays for QFV_CreateResource (and
they need to be kept around for QFV_DestroyResource), it really eases
calculation of memory object size and sub-resource offsets. And
destroying all the objects is just one call to QFV_DestroyResource.
