search-input-file vs (assoc-ref inputs)

[Leo Famulari]

I noticed that, as part of the transition to the new inputs style [0],
we are sometimes replacing code like (assoc-ref inputs "foo") with
(search-input-file inputs "/bin/foo").

I think that we should instead replace the old style with gexps that
specify which package, in order to keep the equivalent functionality.

Otherwise, we risk regressions, when the code finds a match for the
desired filename in the wrong input.

I would say that (search-input-file) is a replacement for the Guile
(which) procedure.

On the other hand, we can replace (assoc-ref inputs ...) with
(this-package-input "foo").

What do you think?

[0] https://guix.gnu.org/en/blog/2021/the-big-change/