Merge pull request #1895 from TheBlueMatt/2022-12-fix-missing-data

Fix some onion errors and assert their length is correct

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

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

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

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