Merge pull request #1611 from TheBlueMatt/2022-07-lower-bounded-estimator-nit

Use a separate (non-trait) fee-estimation fn in LowerBoundedEstimator

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

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

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

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