Hope select function, "top_k" and "bottom_k", could support "group by level"

### Discussed in https://github.com/apache/iotdb/discussions/3888

I find we can use `group by level` to get the effect of merging devices when using aggregation function. Hope select function, `top_k` and `bottom_k`, could support `group by level` as well.

Start with the linked discussion at https://github.com/apache/iotdb/discussions/3888 and compare the existing `group by level` behavior for aggregation functions with `top_k` and `bottom_k`. Done means the two select functions support grouping by level with behavior consistent with aggregation queries, including the case illustrated in the issue.

Written by the indexing model from the issue text.