Significantly reduce thread abuse for faster model moving

This will move all major gradio calls into the main thread rather than random gradio threads.
This ensures that all torch.module.to() are performed in main thread to completely possible avoid GPU fragments.
In my test now model moving is 0.7 ~ 1.2 seconds faster, which means all 6GB/8GB VRAM users will get 0.7 ~ 1.2 seconds faster per image on SDXL.

modules/launch_utils.py

@@ -511,6 +511,11 @@ def start():
     else:
         webui.webui()
 
+    from modules_forge import main_thread
+
+    main_thread.loop()
+    return
+
 
 def dump_sysinfo():
     from modules import sysinfo