LibJS: Tweak FunctionPrototype::to_string and constructors

The output of FunctionPrototype::to_string is now more in line
with the output in Firefox. The builtin constructors have been
extended to include their function name in the output.

Libraries/LibJS/Runtime/NumberConstructor.cpp

@@ -37,6 +37,7 @@
 namespace JS {
 
 NumberConstructor::NumberConstructor()
+    : NativeFunction("Number")
 {
     put_native_function("isSafeInteger", is_safe_integer, 1);