Revert #12461 -- add salt_data kwarg instead

After testing by @jasonrm the previous refactor in 1525f211 didn't quite work as expected, so I've reverted those changes and instead have added a new kwarg to the render function that will control if the function returns salt data or the composed scope for reuse elsewhere as suggested in the salt-users discussion.

Sorry @thatch45, we should've tested this more before I submitted the last PR. My bad.

@jasonrm -- can you install from my revert_12461 branch and confirm this is working for you before this one is merged.