Summary:
Before this diff, Flipper showed *leaf* views created by ComponentKit, but not any intermediate views. Now we show both.
A new node type `SKComponentMountedView` is used for this purpose. Its descriptor `SKComponentMountedViewDescriptor` mostly delegates to its view's descriptor, but redirects back into ComponentKit for children.
Reviewed By: Andrey-Mishanin
Differential Revision: D21130997
fbshipit-source-id: b3c12ea7cc1200962b3ba7c269c48d68b1809948
