1. Add tests ensuring VBO binding with format requiring conversion in
vulkan backend is converted correctly after binding and offset changes.
2. Add tests ensuring VBO binding switching between CPU and GPU handles
correctly in vulkan. As for vulkan, it transfers CPU side memory into
tightly packed buffer and may causing a stride change.

Bug: angleproject:3256
Change-Id: I5d9d78670b28bec286b96d3b6a9c6211da3f3d9b
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1716614
Commit-Queue: Jiacheng Lu <lujc@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>