Merge pull request #1068 from TheBlueMatt/2021-09-ser-cleanup

Simplify Message Serialization and Parse TLV Suffix

diff --cc fuzz/src/chanmon_consistency.rs
Simple merge

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

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

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

diff --cc lightning/src/util/ser.rs
Simple merge

diff --cc lightning/src/util/ser_macros.rs
Simple merge

diff --cc lightning/src/util/test_utils.rs
Simple merge