mtmd: add llama-mtmd-debug binary (#20508)

* mtmd: add llama-mtmd-debug binary

* adapt

* fixes

* fix compile error

* fix windows compile error

* rm legacy clip_debug_encode()

* add MTMD_API to fix build

tools/mtmd/debug/mtmd-debug.md

@@ -0,0 +1,25 @@
+# mtmd-debug
+
+## Debugging encode pass
+
+Example of debugging an input gray image (raw, not preprocessed):
+
+```py
+from transformers import AutoModel
+
+model = AutoModel.from_pretrained(...)
+
+def test_vision():
+  img_size = 896 # number of patches per side
+  pixel_values = torch.zeros(1, 3, img_size, img_size) + 0.5 # gray image
+  with torch.no_grad():
+    outputs = model.model.get_image_features(pixel_values=pixel_values)
+  print("last_hidden_state shape:", outputs.last_hidden_state.shape)
+  print("last_hidden_state:", outputs.last_hidden_state)
+
+test_vision()
+```
+
+## Debugging preprocess pass
+
+(TODO)