Cuttlefish RHS Substitutions

This is the first "in the wild" use of Cuttlefish's new Right Hand Side Substitutions.

Check out the change to `ring.state_dir` for an idea of how it's changed, but basically, instead of using `{{platform_data_dir}}` at build time to determine the default, you can now reference `#(platform_data_dir)` which will be evaluated at runtime.

- [ ] CSE love
- [ ] ProdMgmt love
- [ ] Eng love