Merge pull request #2043 from valentinewallace/2023-02-initial-send-path-fails

`PaymentPathFailed`: add initial send error details

diff --cc lightning-background-processor/src/lib.rs
Simple merge

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

diff --cc lightning/src/routing/gossip.rs
Simple merge

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