intel: Drop MSAA and planar fields from the sampler program keys

This deletes the following shader key fields:

• uint32_t compressed_multisample_layout_mask (minor refactoring to eliminate last user with no downside)
• uint32_t msaa_16 (minor downside for blorp, unused elsewhere)
• uint32_t y_u_v_image_mask (all of these are entirely unused)
• uint32_t y_uv_image_mask
• uint32_t yx_xuxv_image_mask
• uint32_t xy_uxvx_image_mask
• uint32_t ayuv_image_mask
• uint32_t xyuv_image_mask
• uint32_t bt709_mask
• uint32_t bt2020_mask
• float scale_factors[32]

This shrinks the size of the keys and cleans up some unnecessary code.