This adds ability for applications to import Android Hardware Buffers
(AHBs) as OpenGL images which in turn can be sampled from and/or
written.

This was specifically tested with the common use case of importing a
buffer created by an media decoder and using that as a texture source to
include that video content on the screen. Tested with:
- Angry Birds 2 video player (for ads) requires YUV conversion.
- Basic Media Decoder example:
    https://github.com/android/media-samples/tree/master/BasicMediaDecoder

Bug: b/155487768
Change-Id: I9255450f81aa4daa2aace7205d4f6c3f225abcca
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2175103
Commit-Queue: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Tim Van Patten <timvp@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>