blorp: Write to depth/stencil images as depth/stencil when possible

Right now, blorp_blit() and blorp_copy() always write using to images as if they are regular color images. This is fine but it means we have to disable HiZ for BLORP blit/copy destinations which isn't great. Instead, we should just write to gl_FragDepth for depth buffers and use stencil export on Gen9+ for stencil. On Gen12, this removes our one need for CCS resolves for stencil buffers.