mpkg: do_list_installed: use pkg_get_[needs|required_by].
mpkg: do_list_installed: use pkg_get_[needs|required_by].

The function list-installed now prints needed and required packages.

Signed-off-by: Gaël PORTAY <1666f60cfa201a60b0ea694168a0b6932673170a@gmail.com>

gazoo74/mpkg,gazoo74/mpkg