Go back to individual cache props for statics

Summary: This diff is a prereq for experimenting with using individual props for instance methods when there are <N of them. It accomplishes a few things:
- Centralize the prop creation logic to make that experiment easier
- Go back to individaul props for statics. Statics almost certainly didn't contribute to the memory regression, and there tend to be only a couple per class so the extra layer was probably a negative
- Eliminates a local when using shared props in favor of emitting the int directly which should make that scenario slightly more efficient.

Reviewed By: @jano

Differential Revision: D1659983

Signature: t1:1659983:1415835257:6e1f6b6230da8b9637049b0d50087ca321e1f428