Support tracking lifetime of component

[skyfe79]

Motivation

• We need to track the lifetime of the component. For example, when we have video content, we need to play or stop the video depending on the component life.

Changes

• rename DataSource to ListKitDataSource.
• Define func willDisplay(content: Content) on Component.
• Define func didEndDisplay(content: Content) on Component.
• Change visibility of AnyComponent from internal to public.
• Define ComponentLifeTimeTrackingDelegate to track the lifetime of the component and notify it to the component.