Rework the "My PR" page so it does not pull so many info at once
This also adds pagination too, also to reduce the amount of data
retrieved from the DB and thus lower the amount of HTML to generate and
send back.
Fixes https://pagure.io/fedora-infrastructure/issue/9165 (hopefully)
Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>