maint: consistently free hash structures in dev mode

maint: consistently free hash structures in dev mode

Ensure we call hash_free() to avoid valgrind and leak_sanitizer
"definitely lost" warnings.  These were not real leaks as
we terminate immediately after, but we should avoid these
"definitely lost" warnings where possible.

* src/copy.c: Add dest_info_free() and src_info_free().
* src/copy.h: Declare the above.
* src/cp-hash.c: Don't define unless "lint" is defined.
* src/install.c: Call dest_info_free() in dev mode.
* src/mv.c: Likewise.
* src/cp.c: Likewise. Also call src_info_free().
* src/ln.c: Call hash_free() in dev mode.
* src/tail.c: Call hash_free() even if about to exit, in dev mode.

Fixes https://bugs.gnu.org/48189