Fix texture upload format tests:
- Format tests should definitely run on ES3 also.
- Also set filters to NEAREST since some formats aren't filterable.
- Fix RGB9_E5 test reference encoding and add a test for it.
- True int/uint textures require i/usamplers.

Bug: angleproject:2576
Change-Id: Ia5bac34cdee6554a88db339de443689a71a0cf70
Reviewed-on: https://chromium-review.googlesource.com/1068142
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>