[NUI] Remove bindings between Style and View (#1788)

[NUI] Remove bindings between Style and View (#1788)

* [NUI] Remove bindings between Style and View

* [NUI] Hide toast.style

* [NUI] Style of BaseComponent returns copied style.

Style of BaseComponent returns copied style.

* Add API to create ViewStyle from a View instance. (ViewStyle.CopyPropertiesFromView)
* Fix TriggerableSelector to get valid property value from its view.
* BaseComponent may not own style instance so reduce size of selectors in BaseComponents.
* Fix bugs in applying or retreiving style.

Signed-off-by: Jiyun Yang <ji.yang@samsung.com>
Co-authored-by: Jiyun Yang <ji.yang@samsung.com>