Add `outputRows` and `sortTime` metrics to SortExec.

Example output from Ballista:

```
SortExec { input: ProjectionExec { expr: [(Column { name: "l_shipmode" }, "l_shipmode"), (Column { name: "SUM(CASE WHEN
  Metrics: sortTime=44444, outputRows=2
```

Closes #10078 from andygrove/sortexec-metrics

Authored-by: Andy Grove <andygrove73@gmail.com>
Signed-off-by: Andy Grove <andygrove73@gmail.com>