Modify LoadImage node to also traverse subdirectories of the input directory

Previously the LoadImage node only displayed direct file contents.

This change traverses the full directory tree under the `input_dir` using `os.walk`, including symlinks.

nodes.py

@@ -1648,7 +1648,8 @@ class LoadImage:
     @classmethod
     def INPUT_TYPES(s):
         input_dir = folder_paths.get_input_directory()
-        files = [f for f in os.listdir(input_dir) if os.path.isfile(os.path.join(input_dir, f))]
+        strip_inputdir = lambda path: path[len(input_dir)+1:]
+        files = [strip_inputdir(os.path.join(dir,f)) for (dir, subdirs, files) in os.walk(input_dir, followlinks=True) for f in files]
         return {"required":
                     {"image": (sorted(files), {"image_upload": True})},
                 }