cranelift: Port most of simple_preopt.rs over to the peepmatic DSL

This ports all of the identity, no-op, simplification, and canonicalization
related optimizations over from being hand-coded to the `peepmatic` DSL. This
does not handle the branch-to-branch optimizations or most of the
divide-by-constant optimizations.

cranelift/codegen/src/lib.rs

@@ -101,6 +101,7 @@ mod licm;
 mod nan_canonicalization;
 mod num_uses;
 mod partition_slice;
+mod peepmatic;
 mod postopt;
 mod predicates;
 mod redundant_reload_remover;