nir: Add is_sparse flag to texture builders

This sets the is_sparse flag on the resulting nir_tex_instr and the
resulting def to be one component larger.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/40590>

src/compiler/nir/nir_builder.c

@@ -297,6 +297,7 @@ nir_build_tex_struct(nir_builder *build, nir_texop op, struct nir_tex_builder f)
    tex->sampler_dim = dim;
    tex->is_array = is_array;
    tex->is_shadow = false;
+   tex->is_sparse = f.is_sparse;
    tex->backend_flags = f.backend_flags;
    tex->texture_index = f.texture_index;
    tex->sampler_index = f.sampler_index;

src/compiler/nir/nir_builder.h

@@ -2202,6 +2202,7 @@ struct nir_tex_builder {
    enum glsl_sampler_dim dim;
    nir_alu_type dest_type;
    bool is_array;
+   bool is_sparse;
    bool can_speculate;
    uint32_t backend_flags;
 };