cranelift: Remove of/nof overflow flags from icmp (#4879)

* cranelift: Remove of/nof overflow flags from icmp

Neither Wasmtime nor cg-clif use these flags under any circumstances.
From discussion on #3060 I see it's long been unclear what purpose these
flags served.

Fixes #3060, fixes #4406, and fixes #4875... by deleting all the code
that could have been buggy.

This changes the cranelift-fuzzgen input format by removing some IntCC
options, so I've gone ahead and enabled I128 icmp tests at the same
time. Since only the of/nof cases were failing before, I expect these to
work.

* Restore trapif tests

It's still useful to validate that iadd_ifcout's iflags result can be
forwarded correctly to trapif, and for that purpose it doesn't really
matter what condition code is checked.

cranelift/interpreter/src/interpreter.rs

@@ -740,7 +740,7 @@ mod tests {
     #[test]
     fn state_flags() {
         let mut state = InterpreterState::default();
-        let flag = IntCC::Overflow;
+        let flag = IntCC::UnsignedLessThan;
         assert!(!state.has_iflag(flag));
         state.set_iflag(flag);
         assert!(state.has_iflag(flag));