[BUGFIX] Fix globals getting removed after calling a function with the same argument name

[KoloInDaCrib]

Minimal reproduction method:

import funkin.modding.module.Module;

class TestModule extends Module
{
  var thing:String;

  public function onCreate(event:ScriptEvent)
  {
    super.onCreate(event);

    this.test("goomba");
    trace(thing); // Should trace "goomba" but traces null
  }

  function test(thing:String)
  {
    this.thing = thing;
  }
}

This is because in PolymodScriptClass' callFunction function, every variable from interp that wasn't a previously defined variable gets removed, which includes function arguments. Pair that with naming a global variable the same as the function argument, and the result is that the global variable gets its value reset after exiting the function.