management repo symlinks from pkgname.json to pkgbase.json for easy reverse search

There may be different use cases where we want to quickly and directly search for the current pkgbase of a pkgname inside the management repo without the need to iterate over all pkgbase.json files to check for patching pkgname. This could be the case for checks if a to be released package pkgname currently belongs to a different pkgbase and hence avoid edge case problems.

To aid such use cases and have an easier reverse lookup, we can create symlinks from pkgname.json to pkgbase.json.

• Check that we need to clean up pkgname.json symlinks in case a split package part is removed from a pkgbase to avoid having dangling symlinks pointing to a pkgbase that does not provide that pkgname anymore.