T6599: ipsec: support disabling rekey of CHILD_SA.
Also adds support for life_bytes, life_packets, and DPD for
remote-access connections. Changes behavior of remote-access esp-group
lifetime setting to have parity with site-to-site connections.
(cherry picked from commit fd5d7ff0b4fd69b248ecb29c6ec1f3cf844c41cf)