pfsync: Remove deletion of states using the full pfsync_state struct

State deletions are sent over pfsync using struct pfsync_del_c.

Remove the code for receiving state deletions using struct pfsync_state
as such deletions are never sent. Rename functions and constants so that
only the "compressed" versions remain.

Reviewed by: kp
Sponsored by: InnoGames GmbH
Differential Revision: https://reviews.freebsd.org/D40004