refactor($parse): don't use bind-once interceptor for non-bind-once expressions

Side-effects:
  - Logic for allOrNothing watches now lives in $intercept rather than $parse

Closes #9958
I think that is incorrect. $stateful means the output depends on more then just the input, such as `parentValueWatch` depending on `isolateBindingContext`.  This is for the input-watching, nothing to do with bind-once.