Merge pull request #3302 from TheBlueMatt/2024-09-atomic-cleanups

Simplify and fix AtomicCounter

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

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

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

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