* [ASTextNode2] Upgrade lock safety by protecting all ivars (including rarely-changed ones).
Although I don't know of any specific crashes caused by this, I think we should
lock all properties by default. There are also some indications of premature
optimization in keeping lock scope small, where it is actually important to
have transactional integrity, and also where the ASDisplayNode base class is
otherwise going to repeatedly re-lock the object anyway.
I think this will remain pretty efficient, especially with os_unfair_lock enabled.
* Use compare-assign macros
* Introduce ASRecursiveUnfairLock and tests
* Document it and put underscores to scare people away
* Increment changelog
* Integrate it with ASDN::Mutex behind experiment
* Rename the experiment
* Love these license headers oh so much
* Move internal header because we have to
* Address Jon's feedback
* Make display node, layout spec, and style conform to NSLocking so that users/subclasses can access their locks
* Update the changelog
* Align slashes
* Put it back, when we're in ASDisplayNode
* Go a little further
* Put back the changes I didn't mean to commit
* Kick the CI
* Fix yoga build
* Put back non-locking change
* Address comments from Scott
* Fix crashes caused by failing to unlock or destroy a static mutex while the app is being terminated
* Allocate static mutexes on the heap memory to avoid destruction at app exit
* ASThread to use ASDisplayNodeCAssert() instead of assert()
