Change log for PULSE_SECURE_VPN

Date Changes
2022-04-13 Enhancement-Added mappings for new fields in GENERIC_EVENT event_type:
- user_ip to event.idm.read_only_udm.principal.ip.
- user_group_identifier to event.idm.read_only_udm.target.user.group_identifiers.
Modified timestamp in all the event_type to include timezone.
Modified field user_ip, target_ip for GENERIC and NETWORK_CONNECTION event types.