Merge pull request #1121 from TheBlueMatt/2021-10-return-temp-id

Expose temporary channel ID and user channel ID pre-funding

diff --cc fuzz/src/router.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/routing/router.rs
Simple merge