Merge pull request #1004 from TheBlueMatt/2021-07-forward-event

Add a `PaymentForwarded` Event

diff --cc lightning/src/chain/channelmonitor.rs
Simple merge

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

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

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

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

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

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

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