llama : second attempt to refactor vision API

[ngxson]

Fix #8010

Supersede #9687

To test this, please refer to #9687 to convert the model to GGUF.

Then,

cmake --build build -j --target llama-vision
./build/bin/llama-vision -m ../models/llava-1.5-7b-hf/model.gguf --image ../models/bliss.png

# The image showcases a lush green field with a hill in the background. In the foreground, there is a large,
# bright, and vibrant green field with a Microsoft Windows XP desktop screen, possibly representing a
# screensaver, superimposed onto the scene. The field is expansive and covers most of