Allow round-trip via `freeze` command (#1936)
## Summary
We're printing the `Display` representation of `InstalledDist`, which
isn't guaranteed to be (and in fact isn't) a valid PEP 508 requirement,
making it impossible to use the `freeze` output as an input to an
install.
Closes https://github.com/astral-sh/uv/issues/1931.
