[SPARK-20437][R] R wrappers for rollup and cube

## What changes were proposed in this pull request?

- Add `rollup` and `cube` methods and corresponding generics.
- Add short description to the vignette.

## How was this patch tested?

- Existing unit tests.
- Additional unit tests covering new features.
- `check-cran.sh`.

Author: zero323 <zero323@users.noreply.github.com>

Closes #17728 from zero323/SPARK-20437.