Optimize model loader

Child classes only get populated to __subclassess__ when they are imported. We don't actually need to import any of them to webui any more, so clean up webUI imports and make sure loader imports children.

Also, fix command line paths not actually being passed to the scalers.

webui.py

@@ -1,28 +1,21 @@
 import os
-import threading
-
-from modules import devices
-from modules.paths import script_path
 import signal
 import threading
-import modules.paths
+
 import modules.codeformer_model as codeformer
-import modules.esrgan_model as esrgan
-import modules.bsrgan_model as bsrgan
 import modules.extras
 import modules.face_restoration
 import modules.gfpgan_model as gfpgan
 import modules.img2img
-import modules.ldsr_model as ldsr
 import modules.lowvram
-import modules.realesrgan_model as realesrgan
+import modules.paths
 import modules.scripts
 import modules.sd_hijack
 import modules.sd_models
 import modules.shared as shared
-import modules.swinir_model as swinir
 import modules.txt2img
 import modules.ui
+from modules import devices
 from modules import modelloader
 from modules.paths import script_path
 from modules.shared import cmd_opts