src.ctf.fs: make ctf_fs_ds_file_info_create return a unique_ptr

src.ctf.fs: make ctf_fs_ds_file_info_create return a unique_ptr

Introduce ctf_fs_ds_file_info::UP, make ctf_fs_ds_file_info_create
return it.  We don't need a custom deleter, because ctf_fs_ds_file_info
can simply be deleted.  ctf_fs_ds_file_info_destroy will disappear in
the next patches.

Change-Id: Iae4fdf68035d45762f2606685f712fd12976f008
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/8249
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/12287