NVIDIARerank add http_client parameter to pass custom clients (#17832)

...ocessor/llama-index-postprocessor-nvidia-rerank/README.md

...ia-rerank/llama_index/postprocessor/nvidia_rerank/base.py

...or/llama-index-postprocessor-nvidia-rerank/pyproject.toml

...a-index-postprocessor-nvidia-rerank/tests/test_api_key.py

...ostprocessor-nvidia-rerank/tests/test_available_models.py

...-index-postprocessor-nvidia-rerank/tests/test_base_url.py

...r-nvidia-rerank/tests/test_postprocessor_nvidia_rerank.py

...-index-postprocessor-nvidia-rerank/tests/test_truncate.py