Pipeshift llama index integration (#16610)

docs/docs/api_reference/llms/pipeshift.md

docs/docs/examples/llm/pipeshift.ipynb

docs/docs/module_guides/models/llms/modules.md

docs/mkdocs.yml

llama-index-cli/llama_index/cli/upgrade/mappings.json

llama-index-core/llama_index/core/command_line/mappings.json

...x-integrations/llms/llama-index-llms-pipeshift/.gitignore

...-index-integrations/llms/llama-index-llms-pipeshift/BUILD

...dex-integrations/llms/llama-index-llms-pipeshift/Makefile

...ex-integrations/llms/llama-index-llms-pipeshift/README.md

...ama-index-llms-pipeshift/llama_index/llms/pipeshift/BUILD

...dex-llms-pipeshift/llama_index/llms/pipeshift/__init__.py

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

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

...-integrations/llms/llama-index-llms-pipeshift/tests/BUILD

...rations/llms/llama-index-llms-pipeshift/tests/__init__.py

...s/llama-index-llms-pipeshift/tests/test_llms_pipeshift.py