* [REF-2265] ComponentState: scaffold for copying State per Component instance
Define a base ComponentState which can be used to easily create copies of the
given State definition (Vars and EventHandlers) that are tied to a particular
instance of a Component (returned by get_component)
* Define `State` field on `Component` for typing compatibility.
This is an Optional field of Type[State] and is populated by ComponentState.
* Add integration/test_component_state.py
Create two independent counters and increment them separately
* Add unit test for ComponentState
