Avoid enforcing URL correctness for installed distributions (#1793)
## Summary
Allows the corresponding `pypi_types` struct to use any URL, since other
installers can put those into the environment, and Poetry seems to write
invalid URLs.
If we see a distribution with an invalid URL, we just treat it as a
registry distribution, which isn't ideal, but is better than (1)
erroring, and (2) changing `Url` to `String` everywhere internally. (I'm
torn on this second option.)
Closes https://github.com/astral-sh/uv/issues/1744.
## Test Plan
- Added `flask = { git = "git@github.com:pallets/flask.git", rev =
"b90a4f1f4a370e92054b9cc9db0efcb864f87ebe" }` to
`scripts/editable-installs/poetry_editable/pyproject.toml`.
- Ran `poetry install`.
- Ran `cargo pip freeze`. Verified that it errored on `main`, but passed
here.
- Ran `cargo run pip install "flask==3.0.0"`. Verified that it
uninstalled the existing Flask, and installed a new version from the
registry.
