make existing script loading and new preload code use same code for loading modules

limit extension preload scripts to just one file named preload.py

modules/script_loading.py

@@ -0,0 +1,34 @@
+import os
+import sys
+import traceback
+from types import ModuleType
+
+
+def load_module(path):
+    with open(path, "r", encoding="utf8") as file:
+        text = file.read()
+
+    compiled = compile(text, path, 'exec')
+    module = ModuleType(os.path.basename(path))
+    exec(compiled, module.__dict__)
+
+    return module
+
+
+def preload_extensions(extensions_dir, parser):
+    if not os.path.isdir(extensions_dir):
+        return
+
+    for dirname in sorted(os.listdir(extensions_dir)):
+        preload_script = os.path.join(extensions_dir, dirname, "preload.py")
+        if not os.path.isfile(preload_script):
+            continue
+
+        try:
+            module = load_module(preload_script)
+            if hasattr(module, 'preload'):
+                module.preload(parser)
+
+        except Exception:
+            print(f"Error running preload() for {preload_script}", file=sys.stderr)
+            print(traceback.format_exc(), file=sys.stderr)