Raise bitcoind polling interval

MutinyNet's much longer chain history makes the wallet's mempool
handling noticeably more expensive. Recent work moved that work off the
async executor to improve the runtime performance but a single poll can still
consume nearly the full 2 second interval creating constant CPU pressure.

Raise the interval to 10 seconds as a temporary mitigation. It reduces
steady background CPU load without changing the underlying behavior,
and buys time until the BDK performance issue is fixed.

Author: amackillop

src/chain/bitcoind.rs

@@ -41,7 +41,7 @@ use crate::logger::{log_bytes, log_error, log_info, log_trace, LdkLogger, Logger
 use crate::types::{ChainMonitor, ChannelManager, DynStore, Sweeper, Wallet};
 use crate::{Error, NodeMetrics};
 
-const CHAIN_POLLING_INTERVAL_SECS: u64 = 2;
+const CHAIN_POLLING_INTERVAL_SECS: u64 = 10;
 const CHAIN_POLLING_TIMEOUT_SECS: u64 = 10;
 
 pub(super) struct BitcoindChainSource {