opt(frontend): Permute state keys that contain Watermark column

[jon-chuang]

If there is no requirement on the ordering of a state key, we may want to permute keys for stateful operators so that watermark columns are the first column. This allows us to easily perform state cleaning in downstream operators such as HashAgg and HashJoin.

To achieve this, we may have an optimization pass that walks the child nodes of a Watermark-emitting operator such as WatermarkFilter and attempt to permute the group by and join keys.