Add common infrastructure for defining a Scene

Define a simple DSL for defining a scene of SurfaceControls.

For example:

val rootScene = scene {
  content { data ->
      // Make a RenderNode
  }
  ...
  // Add more child scenes
  scene {
      ...
  }
  ...
}

Internally, a Scene will build a tree of SurfaceControls and push
content to the display.

Bug: 405591499
Flag: EXEMPT test only
Test: apk runs locally
Change-Id: I9e6ebf9d32967e21a45fc9e3a1f4a71866062a7b