ANGLE calls WindowSurfaceVk::nextSwapchainImage() to prepare for
the next frame, which allocates an image (and other resources,
like semaphore). However, it's possible for
egl::Display::destroySurface() to be called before the next
submitFrame(), which prevents the image from being returned back
to the swapchain.

This fix refactors swapImpl() to separate out the present work, which
can be called as part of destroy() to return the allocated resources.

dEQP-EGL.functional.query_context.get_current_context.*
dEQP-EGL.functional.query_context.get_current_display.*
dEQP-EGL.functional.query_context.get_current_surface.r*
dEQP-EGL.functional.query_context.query_context.*

Bug: angleproject:3057
Change-Id: Ia943f2530e4f27d1a10ee907e810f0bbdb3bfa9a
Reviewed-on: https://chromium-review.googlesource.com/c/1474601Reviewed-by: Ian Elliott <ianelliott@google.com>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>