Each input pattern can have a predicate in addition to an opcode being
matched. When an opcode has multiple patterns, execute the first pattern
with a true predicate.
The predicates can be type checks or instruction predicates checking
immediate fields.
* Reduce code duplication in TypeConstraint subclasses; Add ConstrainWiderOrEqual to ti and to ireduce,{s,u}extend and f{promote,demote}; Fix bug in emitting constraint edges in TypeEnv.dot(); Modify runtime constraint checks to reject match when they encounter overflow
* Rename Constrain types to something shorter; Move lane_bits/lane_counts in subclasses of ValueType; Add wider_or_eq function in rust and python;
