All usage of GetPointerFromVMA is to recover the pointer that is nulled by changing page type to RasterizerCachedMemory. Our rasterizer cache only works on linear heap and vram, so we can recover the pointer directly by address computation, instead of going through VMA table. Also removed a sanity check pointer!=nullptr in RasterizerMarkRegionCached(RasterizerCachedMemory=>Memory), as now the pointer is never null. The sanity check was added in f2a5a77 (#2797), which was originally necessary during VMA unmapping process, because the function is invloked by VMA after unmapping the page, which in turn invokes back to query the memory, forming a circular dependency. Now the dependency is resolved so the check is not necessary