spirv_to_dxil: Run nir_lower_tex during compilation
This MR fixes a case compiling WGSL shaders where
params.lod_or_sample ends up
emit_texture_size causes a crash while checking argument types in
This was discovered while running the
dawn_end2end_tests's MultisampledSamplingTests.SamplePositions test with Mesa.
Below is some NIR assembly that can cause this:
vec1 32 ssa_18 = deref_var &tint_symbol (uniform sampler2DMS) vec2 32 ssa_21 = (int32)txs ssa_18 (texture_deref), 0 (sampler)