Chaining of submit semaphores is only needed for window surfaces because they
are required for the first usage of the swap chain image and final present
of the image.

Move ownership of the submit semaphores from RendererVk to WindowSurfaceVk and
update all calls to finish and flush to be piped through a ContextVk which
tracks the currently bound window surface.

BUG=angleproject:2464

Change-Id: I4b3083124d7910a5dee297afc219e3a3f28057f2
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1542257
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>