This change adds dirty bit state change tests for image textures.
Meanwhile, syncImages related codes are removed since syncTextures will do
all texture states sync.

Bug: angleproject:3015

Change-Id: I9b299c86af1d589e72c08c5d7c55ac74cc7833aa
Reviewed-on: https://chromium-review.googlesource.com/c/1390596
Commit-Queue: Jiajia Qin <jiajia.qin@intel.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>