Merge pull request #2127 from TheBlueMatt/2023-03-payment-metadata

Support sending `PaymentMetadata` in HTLCs

diff --cc lightning-invoice/src/lib.rs
Simple merge

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

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

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