Perform general code/project maintenance.

• Determine what vendor packages are unused and too costly to maintain. Decide if they should be deprecated or converted to independent projects. Move them out of the Cirq repository.
• Improve developer tools and experience. Use ruff for fast linting and formatting. Check if we are approaching PyPI storage limits; if so, switch to a daily or weekly dev-release cadence.
• Keep third_party/py/cirq and third_party/py/cirq_google modules operational and weekly-updated.