LibJS: Consolidate error messages into ErrorTypes.h

Now, exceptions can be thrown with
interpreter.throw_exception<T>(ErrorType:TYPE, "format", "args",
"here").

Libraries/LibJS/Tests/update-expressions-basic.js

@@ -5,7 +5,7 @@ try {
         ++x;
     }, {
         error: ReferenceError,
-        message: "'x' not known"
+        message: "'x' is not defined",
     });
 
     var n = 0;