[Mesa-dev] Indirect fixes for Samplers

[Timothy Arceri]

The following patch series fixes the indirect sampler indexing piglit tests
 /tests/spec/arb_gpu_shader5/execution/sampler_array_indexing/* for nir.
It also takes steps toward removing the use of the UniformHash table.

There are no piglit regressions and I've also sent a couple more meaner
indirect tests to the piglit list [1].

The nir patch itself has some small problems that I'm requesting feedback on
(see patch 3).

Patch 4 is a related clean-up that is optional but gets us a step closer to
removing the UniformHash hash table.

[1] https://patchwork.freedesktop.org/patch/58063/