List --rdepends for not-installed packages

Using --rdepends for packages that were not installed yielded empty results. Show reverse dependencies for all packages, including those not available.

This changes the default behaviour, and apk info --rdepends will now include reverse dependencies that are not installed too.

The previous behaviour can be achieved by including --installed. E.g.:

$ apk info --rdepends musl | wc -l
11225
$ apk info --from installed --rdepends musl | wc -l
783

See: #11010