Upgrade kf_config.json to v2 (nested config + weight_dtype)

kf_config.json

@@ -1,12 +1,24 @@
 {
   "library_name": "kerasformers",
-  "kerasformers_version": "1.1.3",
+  "kerasformers_version": "1.2.1",
   "model_module": "kerasformers.models.mobilevitv2",
   "model_class": "MobileViTV2ImageClassify",
   "variant": "mobilevitv2_175_cvnets_in1k",
   "weights": "model.weights.h5",
+  "schema_version": 2,
+  "weight_dtype": "float32",
   "model_type": "mobilevitv2",
-  "multiplier": 1.75,
-  "image_size": 256,
-  "num_classes": 1000
+  "vision_config": {
+    "multiplier": 1.75,
+    "image_size": 256,
+    "num_classes": 1000,
+    "output_stride": 32,
+    "atrous_rates": [
+      6,
+      12,
+      18
+    ],
+    "aspp_out_channels": 512,
+    "aspp_dropout_prob": 0.1
+  }
 }