Make bdk and bdk_chain work under 1.57.0

- rewrite some parts of the code to deal with older borrow checker
- downgraded hashbrown

crates/chain/tests/test_keychain_txout_index.rs

@@ -253,7 +253,7 @@ fn test_wildcard_derivations() {
 
     (0..=15)
         .into_iter()
-        .chain([17, 20, 23].into_iter())
+        .chain(vec![17, 20, 23].into_iter())
         .for_each(|index| assert!(txout_index.mark_used(&TestKeychain::External, index)));
 
     assert_eq!(txout_index.next_index(&TestKeychain::External), (26, true));