glsl: remove dead uniforms in nir
This is possible since we now do uniform linking via a nir based linker.
Shader-db results for IRIS (SKL): total instructions in shared programs: 14947192 -> 14946397 (<.01%) instructions in affected programs: 39498 -> 38703 (-2.01%) helped: 230 HURT: 18 total cycles in shared programs: 324868402 -> 324847058 (<.01%) cycles in affected programs: 706701 -> 685357 (-3.02%) helped: 599 HURT: 449
This series causes some CTS test failures but it turns out that it exposed some CTS bugs. All CTS bugs now have there fixes merged upstream.