Summary:
@public
Adds the ability to opt into avoiding global weak JNI refs via `YogaConfig`.
Note that only homogeneous trees are supported, i.e. **mixing weak-ref and non-weak-ref nodes will break!**
Not using JNI refs hopefully will help with avoiding JNI reference table overflows, and will help creating trees on multiple threads, as no lock has to be acquired at any time.
Reviewed By: SidharthGuglani
Differential Revision: D14151037
fbshipit-source-id: 56d94713d39aee080d54be4cb4cdf5e3eccb473a
05f36a835a