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
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>
> 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.
>

Maybe it is about time for `$parse` to be split into
* expression parsing and evaluation
* one-time binding and other enhancements