[core] allow fine-grained setting of message timers

[spencersevilla]

Right now the timeout/retransmit values for all message types (GTP, PFCP, SBI) are set to message.duration (default value 10sec). Having all these timers set to the same value can create weird race-conditions when something times out; to this point the 3GPP specifically recommends fine-tuning these parameters to appropriate values. For example, mme->sgwc GTPv2 messages should naturally have a longer timeout than sgwc->smf GTPv2 messages, which in turn should have a longer timeout than sgwc->sgwu PFCP messages.

This PR removes this limitation by breaking up the message.duration parameter into (gtp_duration, sbi_duration, pfcp_duration), each of which can be set individually.

[github-actions[bot]]

As there has been no recent activity on this PR, it has been marked as stale. It will be automatically closed if no further action is taken.

[github-actions[bot]]

As there has been no recent activity on this PR, it has been marked as stale. It will be automatically closed if no further action is taken.