crocus: fixup large resource allocation better.

max-texture-size was crashing for a couple of reasons.

The first is that on gen8 and under the max surface size is limited, and this would hit an assert rather than the correct failure path. Just call the failure path. @kwg I think iris on gen8 might be broken similiarly.

The second is more of a heuristic, the tests calls tex subimage and that path tries to blit from a staging texture. however it makes sense that if you need to fit both staging and dest textures in the aperture, so if you try to create a staging texture taking up too much space, just fail it, and have the paths fallback properly.