Simplify saving CP state

Rather than makring some parts of VertexLoaderManager dirty in some places and some in others, do it all in VideoState. Also, since CPState no longer contains pointers/non-CP data after d039b1bc0d, we can just use p.Do on it instead of manually saving each field.

Source/Core/VideoCommon/VertexManagerBase.cpp

@@ -557,10 +557,6 @@ void VertexManagerBase::DoState(PointerWrap& p)
   {
     // Flush old vertex data before loading state.
     Flush();
-
-    // Clear all caches that touch RAM
-    // (? these don't appear to touch any emulation state that gets saved. moved to on load only.)
-    VertexLoaderManager::MarkAllDirty();
   }
 
   p.Do(m_zslope);