Verification Intermediate Representation

This crate defines two intermediate representations for verifying ISLE rules.

The core, lower-level Verification IR defined typed expressions for bitvectors, booleans, and integers. The higher-level Annotation IR src/annotation_ir.rs only requires types on some expressions (currently, constants and function definitions) and has some syntactic sugar for easier bitvector conversions (currently, VIRExpr::BVConvTo and VIRExpr::BVConvFrom)