refactor(persist): update file_store, sqlite, wallet to use bdk_chain::persist

Also update examples and remove bdk_persist crate.

example-crates/example_electrum/src/main.rs

@@ -3,6 +3,7 @@ use std::{
     sync::Mutex,
 };
 
+use bdk_chain::persist::PersistBackend;
 use bdk_chain::{
     bitcoin::{constants::genesis_block, Address, Network, Txid},
     collections::BTreeSet,
@@ -351,7 +352,6 @@ fn main() -> anyhow::Result<()> {
     };
 
     let mut db = db.lock().unwrap();
-    db.stage(db_changeset);
-    db.commit()?;
+    db.write_changes(&db_changeset)?;
     Ok(())
 }