Use rank-local caching instead of process-local caching.

Questions for the review:

[ ] Is the scope and purpose of the PR clear?
- [ ] The PR should have a description.
- [ ] The PR should have a guide if needed (e.g., an ordering).
[ ] Is every top-level method and class documented? Are things that should be documented actually so?
[ ] Is the interface understandable? (I.e. can someone figure out what stuff does?) Is it well-defined?
[ ] Does the implementation do what the docstring claims?
[ ] Is everything that is implemented covered by tests?
[ ] Do you see any immediate risks or performance disadvantages with the design? Example: what do interface normals attach to?

illinois-ceesd / mirgecom