RSX: Fix Visual studio debug runtime

[Megamouse]

• Move entire creation of QOffscreenSurface to main thread (assert due to signal from wrong thread)
• Fix invalid ranged_map iterator comparison (assert due to different iterator types).
  This happens if m_it is not set to an iterator of the same object as other.m_it.

iterator it1 = obj1.find(...);
iterator it2 = obj2.find(...);
iterator def1 = {};
iterator def2 = {};

 it1 == def1       // assert
 it1 == it2        // assert
def1 == def2       // fine
 it1 == obj1.end() // fine

[kd-11]

This really doesn't make sense. What exactly is asserting?

[Megamouse]

For reference: you can't compare two iterators if they are not iterators of the same object.
You can only compare iterators of the same object, or e.g. two default iterators.