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/intel/compiler/brw_nir.c

@@ -845,6 +845,7 @@ brw_preprocess_nir(const struct brw_compiler *compiler, nir_shader *nir,
       .lower_txs_lod = true, /* Wa_14012320009 */
       .lower_offset_filter =
          devinfo->verx10 >= 125 ? lower_xehp_tg4_offset_filter : NULL,
+      .lower_invalid_implicit_lod = true,
    };
 
    OPT(nir_lower_tex, &tex_options);
@@ -1308,6 +1309,7 @@ brw_nir_apply_sampler_key(nir_shader *nir,
    nir_lower_tex_options tex_options = {
       .lower_txd_clamp_bindless_sampler = true,
       .lower_txd_clamp_if_sampler_index_not_lt_16 = true,
+      .lower_invalid_implicit_lod = true,
    };
 
    /* Iron Lake and prior require lowering of all rectangle textures */