iris: fix some fast clear bugs, avoid resolves on copy_region-based transfer maps
This series fixes a couple of bugs with fast clears and blorp_copy, and then drops resolves on transfer maps that end up using a GPU copy.
On one Intel-internal benchmark, which does a lot of repeated TexSubImage to subrectangles of a texture, I was seeing resolves before each texture upload. But they were always being copied in via BLORP, which doesn't need resolves. In one particular frame, this cut 10.5% of the time. Overall the effect was around 1-3%.