Previously, the back-end compiler turn image access into magic uniform
reads and there was a complex contract between back-end compiler and
driver about setting up and filling out those params.  As of this
commit, both drivers now lower image_deref_load_param_intel intrinsics
to load_uniform intrinsics controlled by the driver and lower the other
image_deref_* intrinsics to image_* intrinsics which take an actual
binding table index.  There are still "magic" uniforms but they are now
added and controlled entirely by the driver and that contract no longer
spans components.

This also has the side-effect of making most image use compile-time
binding table indices.  Previously, all image access pulled the binding
table index from a uniform.  Part of the reason for this was that the
magic uniforms made it difficult to decouple binding table indices from
the uniforms and, since they are indexed completely differently
(especially in Vulkan), it was hard to pull them apart.  Now that the
driver is handling both, it's trivial to decouple the two and provide
actual binding table indices.

Shader-db results on Kaby Lake:

    total instructions in shared programs: 15166872 -> 15164293 (-0.02%)
    instructions in affected programs: 115834 -> 113255 (-2.23%)
    helped: 191
    HURT: 0

    total cycles in shared programs: 571311495 -> 571196465 (-0.02%)
    cycles in affected programs: 4757115 -> 4642085 (-2.42%)
    helped: 73
    HURT: 67

    total spills in shared programs: 10951 -> 10926 (-0.23%)
    spills in affected programs: 742 -> 717 (-3.37%)
    helped: 7
    HURT: 0

    total fills in shared programs: 22226 -> 22201 (-0.11%)
    fills in affected programs: 1146 -> 1121 (-2.18%)
    helped: 7
    HURT: 0

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>