iris: Support I915_FORMAT_MOD_Y_TILED_GEN12_MC_CCS

Enable the sampling of media compressed surfaces. This is made possible on TGL due to more capable sampler hardware and a unified CCS layout. Support for rendering into these surfaces is not enabled to avoid loss of compression (see the last commit for more details).

Tested with the ext_image_dma_buf_import-intel_modifier test at piglit!374 (merged).

Supersedes !2282 (closed).