This consolidates all texture allocation into ResourceManager11.
It removes a lot of error checking and resource management code.
In a few places we're storing some redundant information, like in
TextureStorage11, we might store the Format pointer in two places,
or the Texture's size.

BUG=angleproject:2034

Change-Id: I9369e76925a67632c444c662e5667c5ed7875547
Reviewed-on: https://chromium-review.googlesource.com/503252Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>