Vulkan allows a swapchain to be created based off of an older swapchain
that's still presenting, to support seamless window resizing.  The old
swapchain will remain alive (though no image can be acquired from it)
and automatically cleaned once no image is being presented from it.

The retired swapchain can be destroyed once all operations on its images
are completed.  We store the old swapchain next to the serial of
submission that's used for CPU throttling and defer the destroy call
until after `finishToSerial` for that serial is called.

Bug: angleproject:2942
Change-Id: Ic62a5a57b712ffa2b087f5fecde0dc8942194075
Reviewed-on: https://chromium-review.googlesource.com/c/1435634
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>