Summary:
* Now all `RCTViewComponentView` subclasses are required to set `_props` instance variable in the constructor with a default value;
* `RCTViewComponentView`'s `_props` instance variable now has `ShadredViewProps` type (that enforced by `static_assert` in `ConcreteViewShadowNode` template);
* New we use `static_pointer_cast` instead of `dynamic_pointer_cast` for casting props.
Reviewed By: mdvacca
Differential Revision: D9734199
fbshipit-source-id: b0a0939c936f8b5b540fa5fa1e4a2f1037346fc5
Summary: Note: not all scrollview props and features (especially event listeners and imperative calls) are supported yet.
Reviewed By: fkgozali
Differential Revision: D7961868
fbshipit-source-id: 5277674fe976e089fd963066f78e705ad846d78d