chore(chain): Standardise KeychainTxOutIndex return types

The previous commit b9c5b9d08b040faf6c6b2d9b3745918031555b72 added
IndexSpk. This goes further and adds `Indexed` and `KeychainIndexed`
type alises (IndexSpk is Indexed<ScriptBuf>) and attempts to standardize
the structure of return types more generally.

crates/esplora/src/async_ext.rs

@@ -8,7 +8,7 @@ use bdk_chain::{
     local_chain::CheckPoint,
     BlockId, ConfirmationTimeHeightAnchor, TxGraph,
 };
-use bdk_chain::{Anchor, IndexSpk};
+use bdk_chain::{Anchor, Indexed};
 use esplora_client::{Amount, TxStatus};
 use futures::{stream::FuturesOrdered, TryStreamExt};
 
@@ -236,7 +236,7 @@ async fn full_scan_for_index_and_graph<K: Ord + Clone + Send>(
     client: &esplora_client::AsyncClient,
     keychain_spks: BTreeMap<
         K,
-        impl IntoIterator<IntoIter = impl Iterator<Item = IndexSpk> + Send> + Send,
+        impl IntoIterator<IntoIter = impl Iterator<Item = Indexed<ScriptBuf>> + Send> + Send,
     >,
     stop_gap: usize,
     parallel_requests: usize,

crates/esplora/src/blocking_ext.rs

@@ -9,7 +9,7 @@ use bdk_chain::{
     local_chain::CheckPoint,
     BlockId, ConfirmationTimeHeightAnchor, TxGraph,
 };
-use bdk_chain::{Anchor, IndexSpk};
+use bdk_chain::{Anchor, Indexed};
 use esplora_client::TxStatus;
 
 use crate::anchor_from_status;
@@ -217,7 +217,7 @@ fn chain_update<A: Anchor>(
 /// [`KeychainTxOutIndex`](bdk_chain::keychain::KeychainTxOutIndex).
 fn full_scan_for_index_and_graph_blocking<K: Ord + Clone>(
     client: &esplora_client::BlockingClient,
-    keychain_spks: BTreeMap<K, impl IntoIterator<Item = IndexSpk>>,
+    keychain_spks: BTreeMap<K, impl IntoIterator<Item = Indexed<ScriptBuf>>>,
     stop_gap: usize,
     parallel_requests: usize,
 ) -> Result<(TxGraph<ConfirmationTimeHeightAnchor>, BTreeMap<K, u32>), Error> {