Enable inlining of java_lang_Class::oop_size_raw

InstanceMirrorKlass::oop_size can be used heavily by GC. It delegates to java_lang_Class::oop_size_raw, which is a trivial method that unfortunately isn't inlined. Inlining is a net win on binary size and reduces time spent executing InstanceMirrorKlass::oop_size by a third when profiling.