nir/lower_tex: Make the adding a 0 LOD to nir_op_tex in the VS optional.

This controls the whole lowering of "make tex ops with implicit
derivatives on non-implicit-derivative stages be tex ops with an explicit
lod of 0 instead", but it's really hard to describe that in a git commit
summary.

All existing callers get it added except:
- nir_to_tgsi which didn't want it.
- nouveau, which didn't want it (fixes regressions in shadowcube and
  shadow2darray with NIR, since the shading languages don't expose txl of
  those sampler types and thus it's not supported in HW)
- optional lowering passes in mesa/st (lower_rect, YUV lowering, etc)

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Jason Ekstrand <jason.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16156>

src/microsoft/spirv_to_dxil/spirv_to_dxil.c

@@ -718,7 +718,9 @@ spirv_to_dxil(const uint32_t *words, size_t word_count,
    }
 
    NIR_PASS_V(nir, nir_lower_readonly_images_to_tex, true);
-   nir_lower_tex_options lower_tex_options = {0};
+   nir_lower_tex_options lower_tex_options = {
+      .lower_invalid_implicit_lod = true,
+   };
    NIR_PASS_V(nir, nir_lower_tex, &lower_tex_options);
 
    NIR_PASS_V(nir, dxil_spirv_nir_fix_sample_mask_type);