[Impeller] fixes for AHB swapchains. (#161562)

Fixes for a variety of speculative fixes for AHB swapchain issues.
Details TBD while some tests run...


1. Even If the SurfaceControl API is supported, there is no guarantee
that we can import the AHB as there may be a mismatch in the required
memory properties and what is available. Add a validity check to the
texture pool and bail from the swapchain if any are invalid.

2. Rather than submitting a dummy cmd buffer that does a layout
transition, use the final command buffer signal semaphore.

3. Import the render ready semaphore and use it to block the onscreen
command buffer.