Include package mapping information in /api/projects/?distro=<distro> output

[leio]

Issue #344 added support for filtering by distribution, to only get the data useful for the distribution. However this information doesn't include the distro mapped name anywhere, so would still have to query the package one by one from /api/project/<package_id> separately. Please include the "packages" key as seen in /api/project/<package_id> in /api/projects/ as well, at least when distro filter is applied and then at least the mapping values for the found distros. Or if it's not too heavy on performance, just always the same output as /api/project/<package_id> but in that list form for all matching projects is of course fine too.

[onny]

That's a really useful feature. E.g. if I want to search for the package "wayland" which is mapped to "Archlinux".