Step Back should work similarly to Step Over, not Step In

Clarification and motivation

It seems to Step Back currently works similarly to Step In, so the behavior of pressing Step Back and Step Over results in unintuitive behavior. This is more evident in LIGO Debugger.

We should look what DAP says about the behavior of this button and change it if necessary.

Acceptance criteria

• I think this should have a nice property that stepBack n . stepOver n == id and stepBack n . stepOver n == id, i.e., if you press either button N times and then return N times, you end up where you started (assuming you didn't hit a boundary).