clear page cache on transaction failure

This is the first step towards rollback, since we still don't spill
pages with WAL, we can simply invalidate page cache in case of failure.

tests/integration/query_processing/test_write_path.rs

@@ -269,7 +269,6 @@ fn test_wal_checkpoint() -> anyhow::Result<()> {
     }
 
     do_flush(&conn, &tmp_db)?;
-    conn.clear_page_cache()?;
     let list_query = "SELECT * FROM test LIMIT 1";
     let mut current_index = 0;
     run_query_on_row(&tmp_db, &conn, list_query, |row: &Row| {