feat(chain)!: Implement ConfirmationBlockTime

Both `bdk_electrum` and `bdk_esplora` now report the exact block
that the transaction is in, which removes the need for having the
old `ConfirmationTimeHeightAnchor` and `ConfirmationHeightAnchor`.
This PR introduces a new, simpler anchor type that can be modified
to support additional data in the future.

example-crates/example_esplora/src/main.rs

@@ -10,7 +10,7 @@ use bdk_chain::{
     indexer::keychain_txout,
     local_chain::{self, LocalChain},
     spk_client::{FullScanRequest, SyncRequest},
-    ConfirmationTimeHeightAnchor, Merge,
+    ConfirmationBlockTime, Merge,
 };
 
 use bdk_esplora::{esplora_client, EsploraExt};
@@ -26,7 +26,7 @@ const DB_PATH: &str = ".bdk_esplora_example.db";
 
 type ChangeSet = (
     local_chain::ChangeSet,
-    indexed_tx_graph::ChangeSet<ConfirmationTimeHeightAnchor, keychain_txout::ChangeSet<Keychain>>,
+    indexed_tx_graph::ChangeSet<ConfirmationBlockTime, keychain_txout::ChangeSet<Keychain>>,
 );
 
 #[derive(Subcommand, Debug, Clone)]