Scale texture sizes to fit within available memory

Scale texture sizes to fit within available memory

The change makes use of platform-specific information to scale the
dimensions of textures used by the advanced shader image load store
tests so they fit inside available memory.

Affects:

KHR-GL*.shader_image_load_store.advanced-copyImage
KHR-GL*.shader_image_load_store.advanced-memory-order
KHR-GL*.shader_image_load_store.advanced-sso-perSample
KHR-GL*.shader_image_load_store.advanced-sso-simple
KHR-GL*.shader_image_load_store.advanced-sso-subroutine
KHR-GL*.shader_image_load_store.advanced-sync-imageAccess2

Components: OpenGL

VK-GL-CTS issue: 1314

Change-Id: I06e7e4629b0e00f0ca5c152df56c09bbdcc05247