## Summary
This PR revives https://github.com/astral-sh/uv/pull/4944, which I think
was a good start towards adding `--trusted-host`. Last night, I tried to
add `--trusted-host` with a custom verifier, but we had to vendor a lot
of `reqwest` code and I eventually hit some private APIs. I'm not
confident that I can implement it correctly with that mechanism, and
since this is security, correctness is the priority.
So, instead, we now use two clients and multiplex between them.
Closes https://github.com/astral-sh/uv/issues/1339.
## Test Plan
Created self-signed certificate, and ran `python3 -m http.server --bind
127.0.0.1 4443 --directory . --certfile cert.pem --keyfile key.pem` from
the packse index directory.
Verified that `cargo run pip install
transitive-yanked-and-unyanked-dependency-a-0abad3b6 --index-url
https://127.0.0.1:8443/simple-html` failed with:
```
error: Request failed after 3 retries
Caused by: error sending request for url (https://127.0.0.1:8443/simple-html/transitive-yanked-and-unyanked-dependency-a-0abad3b6/)
Caused by: client error (Connect)
Caused by: invalid peer certificate: Other(OtherError(CaUsedAsEndEntity))
```
Verified that `cargo run pip install
transitive-yanked-and-unyanked-dependency-a-0abad3b6 --index-url
'https://127.0.0.1:8443/simple-html' --trusted-host '127.0.0.1:8443'`
failed with the expected error (invalid resolution) and made valid
requests.
Verified that `cargo run pip install
transitive-yanked-and-unyanked-dependency-a-0abad3b6 --index-url
'https://127.0.0.1:8443/simple-html' --trusted-host '127.0.0.2' -n` also
failed.
## Summary
This PR moves all the CLI code into its own crate, separate from the
`uv` crate. The `uv` crate is iterated on frequently, and the CLI code
comprises a significant portion of it but rarely changes. Removing the
CLI code reduces the `uv` crate size from 1.4MiB to 1.0MiB.
Charlie Marsh