Many of the member variables of the thread class aren't even used outside of the class itself, so there's no need to make those variables public. This change follows in the steps of the previous changes that made other kernel types' members private. The main motivation behind this is that the Thread class will likely change in the future as emulation becomes more accurate, and letting random bits of the emulator access data members of the Thread class directly makes it a pain to shuffle around and/or modify internals. Having all data members public like this also makes it difficult to reason about certain bits of behavior without first verifying what parts of the core actually use them. Everything being public also generally follows the tendency for changes to be introduced in completely different translation units that would otherwise be better introduced as an addition to the Thread class' public interface.