Let `iProp` refer to `uPred ... : Type` instead of `uPredO ... : ofeT`
This has two advantages:
- It is more consistent with respect to the rest of the development. Elsewhere we use the
Osuffix for the OFE variant and the version without suffix for the
- It gives a minor speedup of 1.72% overall on LambdaRust, with peaks of 5.77% for individual files. See here.
This MR breaks backwards compatibility, but the number of changes needed are minor. See here for LambdaRust.