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/codegen/src/isa/x64/inst/args.rs

@@ -1659,8 +1659,6 @@ impl CC {
             IntCC::UnsignedGreaterThan => CC::NBE,
             IntCC::UnsignedLessThanOrEqual => CC::BE,
             IntCC::UnsignedLessThan => CC::B,
-            IntCC::Overflow => CC::O,
-            IntCC::NotOverflow => CC::NO,
         }
     }