gguf mistral quantized 2-bit 3-bit 4-bit 5-bit 6-bit 8-bit GGUF text-generation base_model:nvidia/Mistral-NeMo-Minitron-8B-Instruct base_model:quantized:nvidia/Mistral-NeMo-Minitron-8B-Instruct region:us imatrix conversational