fix($parse): standardize one-time literal vs non-literal and interceptors

Previously literal one-time bindings did not use the expression `inputs`, causing infinite digest issues with literal values. This often forces the use of deepEquals when watching one-time literals.

`ng-class` is one example of deepEquals which is no longer required.

This one-time/literal behavior is now also consistently propogated through interceptors.

Closes #15858