nir: Get rid of nir_dest_bit_size()

We could add a nir_def_bit_size() helper but we use ->bit_size about 3x
as often as nir_dest_bit_size() today so that's a major Coccinelle
refactor anyway and this doesn't make it much worse.  Most of this
commit was generated byt the following semantic patch:

    @@
    expression D;
    @@

    <...
    -nir_dest_bit_size(D)
    +D.ssa.bit_size
    ...

Some manual fixup was needed, especially in cpp files where Coccinelle
tends to give up the moment it sees any interesting C++.

Acked-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24674>

src/vulkan/runtime/vk_nir_convert_ycbcr.c

@@ -271,7 +271,7 @@ create_plane_tex_instr_implicit(struct ycbcr_state *state,
    tex->is_array = old_tex->is_array;
 
    nir_def_init(&tex->instr, &tex->dest.ssa, old_tex->dest.ssa.num_components,
-                nir_dest_bit_size(old_tex->dest));
+                old_tex->dest.ssa.bit_size);
    nir_builder_instr_insert(b, &tex->instr);
 
    return &tex->dest.ssa;