[GLESv3] Texture state tracking upgrades

- TextureUtils to get the low down on all offset/size related calculations
(ripped from SwiftShader)
    - This involves track of all PBO fields
- Move TextureRec and friends to GLSharedGroup
- Implement new encoder utils to use in encoder

Change-Id: Ic6585f49d2928fe965181ec706d5fefa8713e0eb