Revert "Implements more pack/unpack states. Pack: row length, skip rows, skip pixels. Unpack: image height, skip images, skip rows, skip pixels."

This is causing failures in dEQP-GLES3.functional.texture.specification.teximage3d_depth_pbo.depth_component24_2d_array

First failing build on the bot:
http://build.chromium.org/p/chromium.gpu.fyi/builders/Win7%20Release%20dEQP%20%28NVIDIA%29/builds/3635

Please fix the failure and re-land your CL with the fix.

BUG=angleproject:512
BUG=angleproject:1095

This reverts commit f1bb3f05.

Change-Id: I30f61db888b0adf73a1d98bbeeb2428068119627
Reviewed-on: https://chromium-review.googlesource.com/304990Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>