This adds the most basic form of rendering feedback loop detection:
when we're rendering to a texture that's also bound as an input. It
doesn't filter by selected mipmap level or 3D texture slice, or
do depth attachment validation. It also is missing checks for feedback
loops against the default Framebuffer.

BUG=angleproject:1685

Change-Id: Idb0ee2bfe1c35611544d132204c0da832c0f1c48
Reviewed-on: https://chromium-review.googlesource.com/425489
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>