DataRef: borrow for great perf (#434)

* DataRef: borrow for great perf

* address review comments

* Optimize `drop_table`, `rename_table`, `delete_by_col_eq`, and `clear_table` (#436)

* optimize delete, drop, rename

* address review comments

* even less cloning

* more refactoring

crates/core/src/db/datastore/locking_tx_datastore/btree_index.rs

@@ -64,12 +64,12 @@ pub struct BTreeIndexRangeIter<'a> {
     range_iter: btree_set::Range<'a, IndexKey>,
 }
 
-impl Iterator for BTreeIndexRangeIter<'_> {
-    type Item = RowId;
+impl<'a> Iterator for BTreeIndexRangeIter<'a> {
+    type Item = &'a RowId;
 
     #[tracing::instrument(skip_all)]
     fn next(&mut self) -> Option<Self::Item> {
-        self.range_iter.next().map(|key| key.row_id)
+        self.range_iter.next().map(|key| &key.row_id)
     }
 }