Merge pull request #2973 from valentinewallace/2024-03-om-mailbox

Support intercepting onion messages for offline peers

diff --cc lightning/src/events/mod.rs
Simple merge

diff --cc lightning/src/onion_message/functional_tests.rs
Simple merge

diff --cc lightning/src/onion_message/messenger.rs
Simple merge

diff --cc lightning/src/onion_message/packet.rs
Simple merge