i965: Implement compute sampler state atom.

i965: Implement compute sampler state atom.

Fixes a number of GLES31 CTS failures and hangs on various hardware:

 ES31-CTS.texture_gather.plain-gather-depth-2d
 ES31-CTS.texture_gather.plain-gather-depth-2darray
 ES31-CTS.texture_gather.plain-gather-depth-cube
 ES31-CTS.texture_gather.offset-gather-depth-2d
 ES31-CTS.texture_gather.offset-gather-depth-2darray
 ES31-CTS.layout_binding.sampler2D_layout_binding_texture_ComputeShader
 ES31-CTS.layout_binding.sampler2DArray_layout_binding_texture_ComputeShader
 ES31-CTS.explicit_uniform_location.uniform-loc-types-samplers
 ES31-CTS.compute_shader.resources-texture

Some of them were actually passing by luck on some generations even
though we weren't uploading sampler state tables explicitly for the
compute stage, most likely because they relied on the cached sampler
state left from previous rendering to be close enough.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92589
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93312
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93325
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93407
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93725
Reported-by: Marta Lofstedt <marta.lofstedt@intel.com>
Reviewed-by: Marta Lofstedt <marta.lofstedt@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>