Randomly draw forwarding delays

Now that we have `BackgroundProcessor` drive the batch forwarding of
HTLCs, we implement random sampling of batch delays from a log-normal
distribution with a mean of 50ms.

Author: tnull

lightning-background-processor/Cargo.toml

@@ -25,6 +25,7 @@ bitcoin-io = { version = "0.1.2", default-features = false }
 lightning = { version = "0.2.0", path = "../lightning", default-features = false }
 lightning-rapid-gossip-sync = { version = "0.2.0", path = "../lightning-rapid-gossip-sync", default-features = false }
 lightning-liquidity = { version = "0.2.0", path = "../lightning-liquidity", default-features = false }
+possiblyrandom = { version = "0.2", path = "../possiblyrandom", default-features = false }
 
 [dev-dependencies]
 tokio = { version = "1.35", features = [ "macros", "rt", "rt-multi-thread", "sync", "time" ] }