nir: Get rid of nir_dest_num_components()

nir: Get rid of nir_dest_num_components()

We could add a nir_def_num_components() helper but we use
ssa.num_components about 3x as often as nir_dest_num_components() 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_num_components(D)
    +D.ssa.num_components
    ...

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>