add function grouping() to identify the result rows for group by cube/rollup/grouping sets #925

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
group by cube/rollup/grouping has many rows result by different group set, we need to
identify them.
Describe the solution you'd like
A groupping function that takes the group by keys as parameters,
return an integer those bits related the group keys used are set to 0 and others set to 1.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.