d/rust-coreutils.install: install to the expected location

Executables are installed to `/usr/lib/cargo/bin/coreutils` in the
Debian package as this is an experimental package, not meant to replace
`coreutils` yet, contrary to what we want for Apertis.

This commit changes the install path of all executables so they are
placed in `/bin` and `/usr/bin`, and can therefore be used system-wide.

Signed-off-by: Arnaud Ferraris <arnaud.ferraris@collabora.com>