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/fuzzgen/src/function_generator.rs

@@ -436,9 +436,7 @@ const OPCODE_SIGNATURES: &'static [(
     (Opcode::Icmp, &[I16, I16], &[B1], insert_cmp),
     (Opcode::Icmp, &[I32, I32], &[B1], insert_cmp),
     (Opcode::Icmp, &[I64, I64], &[B1], insert_cmp),
-    // TODO: icmp of/nof broken for i128 on x86_64
-    // See: https://github.com/bytecodealliance/wasmtime/issues/4406
-    // (Opcode::Icmp, &[I128, I128], &[B1], insert_cmp),
+    (Opcode::Icmp, &[I128, I128], &[B1], insert_cmp),
     // Stack Access
     (Opcode::StackStore, &[I8], &[], insert_stack_store),
     (Opcode::StackStore, &[I16], &[], insert_stack_store),