LibJS: Give argument vectors an inline capacity of 8

This avoids one malloc/free pair for every function call if there are
8 arguments or fewer.

Libraries/LibJS/Runtime/ScriptFunction.cpp

@@ -48,7 +48,7 @@ ScriptFunction::~ScriptFunction()
 Value ScriptFunction::call(Interpreter& interpreter)
 {
     auto& argument_values = interpreter.call_frame().arguments;
-    Vector<Argument> arguments;
+    ArgumentVector arguments;
     for (size_t i = 0; i < m_parameters.size(); ++i) {
         auto name = parameters()[i];
         auto value = js_undefined();