feat: Add new argument for p2p base model path in app.py

- Introduced a new command-line argument `--p2p_base_model_path` to specify the path to the base model for evaluation, defaulting to "timbrooks/instruct-pix2pix". This enhancement allows for greater flexibility in model selection during runtime.

app.py

@@ -28,6 +28,14 @@ def parse_args():
             "The path to the base model to use for evaluation. This can be a local path or a model identifier from the Model Hub."
         ),
     )
+    parser.add_argument(
+        "--p2p_base_model_path",
+        type=str,
+        default="timbrooks/instruct-pix2pix", 
+        help=(
+            "The path to the base model to use for evaluation. This can be a local path or a model identifier from the Model Hub."
+        ),
+    )
     parser.add_argument(
         "--resume_path",
         type=str,