Function before_cursor_execute

test/perf/many_table_reflection.py:398–402

(
        conn, cursor, statement, parameters, context, executemany
    )

    @sa.event.listens_for(engine, "before_cursor_execute")
    def before_cursor_execute(
        conn, cursor, statement, parameters, context, executemany
    ):
        nonlocal now
        now = time.time()

    @sa.event.listens_for(engine, "after_cursor_execute")
    def after_cursor_execute(