Add dynamic Synthesizer LLM node

[georgi]

Summary

• create llms namespace
• add Synthesizer node that renders a Jinja prompt with dynamic properties
• test that Synthesizer sends rendered prompt to the LLM

Testing

• pip install . (fails: Could not find poetry-core)
• nodetool package scan
• nodetool codegen (fails: AssertionError: Field type is not a type)
• black . (fails to parse pyproject.toml)
• ruff check . (fails to parse pyproject.toml)
• mypy . (fails: pyproject.toml parse error)
• flake8
• pytest -q (fails: ModuleNotFoundError: No module named 'nodetool.nodes.llms')