Add back button functionality and auto next/back buttons.

- Refactor/create methods for setting directional callbacks
  ( back, next )
- Refactor setting and checking callbacks in step and stepbuilder
- Automatic back and next buttons when calling next() or back()
- Renamed and added arrow icons.
- Revise test tour with configured back steps

Bug: 55772
Change-Id: I8446bade1def3967d101f34d5b2f711c81c944fc
Merge "Add back button functionality and auto next/back buttons."