Remove interval caching for atomic rules

[Sean Kauffman]

Atomic rules have no reason to cache intervals since they will never look backwards. This is a small optimization but one that can mean atomic rules are lighter weight, which is nice for readability, etc.

Arguably, it’s a bug that atomic rules cache intervals.

Removing the cache will mean reasonably reworking how atomic rules are handled in the algorithm. The compiler should also know not to allocate space for them.