LibJS: Implement the Number::remainder AO using fmod

The ECMA verbiage for modulus is the mathematical definition implemented
by fmod, so let's just use that rather than trying to reimplement all
the edge cases.

Userland/Libraries/LibJS/Tests/test-common.js

@@ -53,6 +53,9 @@ class ExpectationError extends Error {
 
     const valueToString = value => {
         try {
+            if (value === 0 && 1 / value < 0) {
+                return "-0";
+            }
             return String(value);
         } catch {
             // e.g for objects without a prototype, the above throws.