Merge pull request #2907 from shaavan/issue2882

Introduce ResponseInstructions for OnionMessage Handling

diff --cc lightning/src/ln/channelmanager.rs
Simple merge

diff --cc lightning/src/ln/peer_handler.rs
Simple merge

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

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