* chore: remove unused views API classes
* chore: remove LayoutManager code
* chore: no more need to make View inherit from TrackabeObject
* chore: make enable_view_api default to true
* chore: enable_view_api => enable_views_api
Exposing these in the renderer didn't make sense as they weren't backed
by the same instance / value store. This API should be browser only
especially now that we have nativeTheme.themeSource. Exposing in
//common was a mistake from the beginning.
