prefactor: rename bitcoind_rpc to bitcoind

Since we unify RPC and REST sync clients in the
following commit, we rename bitcoind_rpc to bitcoind
as this appropriately captures the unified client.

Author: enigbe

src/chain/bitcoind_rpc.rs renamed to src/chain/bitcoind.rs

@@ -5,10 +5,10 @@
 // http://opensource.org/licenses/MIT>, at your option. You may not use this file except in
 // accordance with one or both of these licenses.
 
-mod bitcoind_rpc;
+mod bitcoind;
 mod electrum;
 
-use crate::chain::bitcoind_rpc::{
+use crate::chain::bitcoind::{
 	BitcoindRpcClient, BoundedHeaderCache, ChainListener, FeeRateEstimationMode,
 };
 use crate::chain::electrum::ElectrumRuntimeClient;