Vulkan: Use serial to check which FBO has open RP In preparation for the scenario where an imageless framebuffer is shared, checking whether the started render pass belongs to a certain framebuffer is tweaked to use a serial-based method instead of checking the framebuffer handle. * Added the last render pass serial to ContextVk, which increments every time a render pass begins. The serial is also stored in the FramebufferVk object invoking it. * Added the type RenderPassSerial for this purpose. * Serials are generated through a serial factory in ContextVk. * Updated hasStartedRenderPassWithSerial() to match the serials instead of the handles. * Removed the getFramebuffer() calls from FramebufferVk and UtilsVk that are now unused. Bug: angleproject:7553 Change-Id: Id60dcbf7973558d35e55ff4af4c71e50c6853bba Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3897970 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Charlie Lao <cclao@google.com> Commit-Queue: Amirali Abdolrashidi <abdolrashidi@google.com>