Implement 'clear_attr' and 'set_attr' opcodes
Fix heinous reaching definitions bug

While implementing 'get_next_prop' opcode a bad bug in the reaching defintions solution was exposed. This resulted in temps not being marked as used correctly within loops.
Lower 'ReadObjectFirstPropertyAddressExpr' and fix bound tree dump bug
A bit of binder refactoring
Move object reads and writes out of lowering and into initial binding, where it's easier to add temps