Adding clang thread safety analysis for ROS2 core packages

[gbiggs]

@emersonknapp

I kept all existing locking logic intact but shifted ownership of the locking around - The main difference is that in favor of a private mutex ownership patterm, I removed the “lock-wrapper” LockedObject pattern, because it spread out locking and safety in such a way that it would be easy to make more mistakes, spreads ownership of safety to any user of the data, instead of centralizing in the thread-accessed data. That may not be the way we want to go, it’s just what seems to make the most sense to me

I haven’t looked at the details, but what you say makes sense from a maintainability point of view.