Move some numeric trait logic to default implementations

There are a handful of functions we can move out of the macro and to the
numeric traits as default implementations; do that here.

Additionally, add some bounds that make sense for completeness.

library/compiler-builtins/libm/crates/libm-test/src/test_traits.rs

@@ -314,7 +314,7 @@ where
         // Make sure that the signs are the same before checing ULP to avoid wraparound
         let act_sig = actual.signum();
         let exp_sig = expected.signum();
-        ensure!(act_sig == exp_sig, "mismatched signs {act_sig} {exp_sig}");
+        ensure!(act_sig == exp_sig, "mismatched signs {act_sig:?} {exp_sig:?}");
 
         if actual.is_infinite() ^ expected.is_infinite() {
             bail!("mismatched infinities");