clip : refactor set input for cgraph + fix qwen2.5vl input

[ngxson]

Refactor clip_image_encode input, using a more fail-proof mechanism. Basically, this refactoring flatten complicated nested if...else conditions into a switch statement.

This also fixes the issue described in #12402 (comment)

Test results:

OK:   llama-mtmd-cli ggml-org/SmolVLM-500M-Instruct-GGUF:Q8_0
OK:   llama-mtmd-cli ggml-org/SmolVLM2-2.2B-Instruct-GGUF:Q4_K_M
OK:   llama-mtmd-cli ggml-org/SmolVLM2-500M-Video-Instruct-GGUF:Q8_0
OK:   llama-mtmd-cli ggml-org/gemma-3-4b-it-GGUF:Q4_K_M
OK:   llama-mtmd-cli guinmoon/MobileVLM-3B-GGUF:Q4_K_M
OK:   llama-mtmd-cli THUDM/glm-edge-v-5b-gguf:Q4_K_M
OK:   llama-mtmd-cli second-state/Llava-v1.5-7B-GGUF:Q2_K
OK:   llama-mtmd-cli cjpais/llava-1.6-mistral-7b-gguf:Q3_K
OK:   llama-mtmd-cli ibm-research/granite-vision-3.2-2b-GGUF:Q4_K_M
OK:   llama-mtmd-cli second-state/MiniCPM-Llama3-V-2_5-GGUF:Q2_K
OK:   llama-mtmd-cli openbmb/MiniCPM-V-2_6-gguf:Q2_K
OK:   llama-mtmd-cli openbmb/MiniCPM-o-2_6-gguf:Q4_0
OK:   llama-qwen2vl-cli bartowski/Qwen2-VL-2B-Instruct-GGUF:Q4_K_M
OK:   llama-qwen2vl-cli ggml-org/Qwen2.5-VL-3B-Instruct-GGUF:Q4_K_M

[ngxson]

Having this check will prevent mistakes like the one from pixtral model, where the size of input std::vector is bigger than the size of the tensor