UseCompressedClassPointers, deprecated with JDK 25 (JDK-8350753), should be removed, and its maintaining code removed as well.

One roadblock before this is the ongoing existence of the two remaining 32-bit platforms: arm32 and zero 32bit. 32-bit platforms rely on -UseCompressedClassPointers, so removing that code will break 32-bit. We need to figure out what to do with those first.