Make scorer decay + persistence more frequent

There's some edge cases in our scoring when the information really
should be decayed but hasn't yet been prior to an update. Rather
than try to fix them exactly, we instead decay the scorer a bit
more often, which largely solves them but also gives us a bit more
accurate bounds on our channels, allowing us to reuse channels at
a similar amount to what just failed immediately, but at a
substantial penalty.

Author: TheBlueMatt

lightning-background-processor/src/lib.rs

@@ -108,7 +108,7 @@ const PING_TIMER: u64 = 1;
 const NETWORK_PRUNE_TIMER: u64 = 60 * 60;
 
 #[cfg(not(test))]
-const SCORER_PERSIST_TIMER: u64 = 60 * 60;
+const SCORER_PERSIST_TIMER: u64 = 60 * 5;
 #[cfg(test)]
 const SCORER_PERSIST_TIMER: u64 = 1;