Savestate: Fix loading kernel heaps and pre-exit-callback states

KernelHeap was missing from CreateByIDType, and an unknown type returned
without an error, desyncing the rest of the load. States from before exit
callbacks kept the boot-time action slot, which sceMpeg's restore took over.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Core/HLE/sceKernelThread.cpp

@@ -849,6 +849,10 @@ void __KernelThreadingDoState(PointerWrap &p)
 	if (s >= 5) {
 		Do(p, actionAfterExitCallback);
 		__KernelRestoreActionType(actionAfterExitCallback, ActionAfterExitCallback::Create);
+	} else {
+		// Older states numbered the action types without this one, so the slot it got at boot may
+		// now be restored to another type (sceMpeg's).  Give it a new one after all of those.
+		actionAfterExitCallback = __KernelRegisterActionType(ActionAfterExitCallback::Create);
 	}
 
 	Do(p, pausedDelays);