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
we've made it harder on users, and we've made it harder on maintainers. this was not the right thing to do, even if it artificially appears faster. seriously, it was bogus, i'm sick of it.