ENH: add option shape to functions in draw v2

This PR replaces #1020


I think the "correct" docstring here would be:

```
rr, cc : (N,) array of int
    Row and column indices of valid pixels (i.e. those inside `shape`).
val : (N,) array of float, optional
    Values at `rr, cc`. Returned only if `val` is given as input.
```