## Summary
This fixes an extremely subtle bug in `pip install --reinstall`, whereby
if you depend on `setuptools` at the top level, we end up uninstalling
it after resolving, which breaks some cached state. If we have
`--reinstall`, we need to reset that cached state between resolving and
installing.
## Test Plan
Running `pip install --reinstall` with:
```txt
setuptools
devpi @ https://files.pythonhosted.org/packages/e4/f3/e334eb4dc930ccb677363e1305a3730003d203efbb023329e4b610e4515b/devpi-2.2.0.tar.gz
```
Fails on `main`, but passes.
Charlie Marsh
e71e3e8dd1