Refactor query in build feed endpoint

We have a problematic query in our build feed endpoint (see https://github.com/AlmaLinux/albs-web-server/blob/master/alws/crud/build.py#L133-L142). This query loads too many entries because of join statements, but without them, filters don't work. Also, we should refactor how we communicate with Pulp too, because currently, we're looking into the whole Pulp for packages. We should refactor these code parts without losing the ability to filter builds and without losing performance.