MistralAI MultImodal content blocks (#17997)

llama-index-core/llama_index/core/base/llms/types.py

...a-index-llms-mistralai/llama_index/llms/mistralai/base.py

...-index-llms-mistralai/llama_index/llms/mistralai/utils.py

...tegrations/llms/llama-index-llms-mistralai/pyproject.toml

...-mistralai/llama_index/multi_modal_llms/mistralai/base.py

...mistralai/llama_index/multi_modal_llms/mistralai/utils.py

...lms/llama-index-multi-modal-llms-mistralai/pyproject.toml

...dal-llms-mistralai/tests/test_multi-modal-llms_mistral.py