ffb8480087
## Summary This PR adds two flags to `pip-sync`: `--reinstall`, and `--reinstall-package [PACKAGE]`. The former reinstalls all packages in the requirements, while the latter can be repeated and reinstalls all specified packages. For our purposes, a reinstall includes (1) purging the cache, and (2) marking any already-installed versions as extraneous. Closes #572. Closes https://github.com/astral-sh/puffin/issues/271.