OverlayAdapter::metadata() leaked a new copy of the manifest display_name on
every call, and the hook router calls it on every hook event, so a manifest
with display_name grew memory for the life of the server. Leak it once when
the overlay is built, as the helper's comment already promised.

Co-authored-by: Lucenx9 <185146821+Lucenx9@users.noreply.github.com>