### What's the problem this feature will solve? The [user-agent string used by pip](https://github.com/pypa/pip/blob/6958e28f366f00373343efcd5a7e776a810cb133/src/pip/_internal/network/session.py#L115) includes things such as cpu, os, os version, etc, that my network admins would prefer not be shared. ### Describe the solution you'd like Adding an option to pip.conf to disable linehaul metadata in the user-agent string. ### Alternative Solutions n/a ### Additional context n/a ### Code of Conduct - [X] I agree to follow the [PSF Code of Conduct](https://www.python.org/psf/conduct/).