TC_pfcp_heartbeat_periodic: verify that the IUT sends periodic PFCP Heartbeat Requests and that the heartbeat timer re-arms correctly after each successful response (at least 2 periodic HBs must be observed).
TC_pfcp_heartbeat_miss_threshold: verify that the IUT resets the PFCP association after mp_pfcp_heartbeat_miss_count consecutive unanswered Heartbeat Requests (a new Association Setup Request is expected).
TC_pfcp_heartbeat_miss_reset: verify that a successful Heartbeat Response resets the miss counter; run 2 cycles of missing (miss_count - 1) HBs then responding to one, expecting no association reset throughout.
TC_pfcp_heartbeat_rts_mismatch: verify that the IUT detects a UPF restart when a Heartbeat Response carries a different Recovery Timestamp than the one observed during Association Setup, and that it promptly resets and re-establishes the PFCP association.
Also add module parameters for the heartbeat configuration (mp_pfcp_heartbeat_interval, mp_pfcp_heartbeat_req_timeout, mp_pfcp_heartbeat_miss_count) and update osmo-s1gw.config accordingly.
