memory alloc: Remove last heaps from memory alloc and requirements

memory alloc: Remove last heaps from  memory alloc  and requirements

Also reorder memory_alloc_info struct as memPriority added back in as last
member in struct.

Conflicts:
	demos/cube.c
	demos/tri.c
	icd/intel/buf.c
	icd/intel/event.c
	icd/intel/img.c
	icd/intel/mem.c
	icd/intel/pipeline.c
	icd/intel/query.c
	include/xgl.h
	tests/image_tests.cpp
	tests/init.cpp
	tests/render_tests.cpp
	tests/xgltestbinding.cpp
	tests/xgltestbinding.h