Putting Serial allocation in the Renderer allows the Helper
classes to manage allocating its own Serial. The init functions for
ImageViewHelper only have access to a vk::Context/RendererVk, not a
ContextVk. This will be updated in a future CL.

Re-uses the Serial Type X-Macro to do more code generation.
Serial allocation now uses an atomic because of its now Renderer
shared location.

Bug: angleproject:4911
Change-Id: I2d5d3d0bbf613d5468de795a700f66164291bc79
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2332884
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Charlie Lao <cclao@google.com>