When we go to install a locked `requirements.txt`, if a wheel is already
available in the local cache, and matches the version specifiers, we can
just use it directly without fetching the package metadata. This speeds
up the no-op case by about 33%.
Closes https://github.com/astral-sh/puffin/issues/48.
This PR modifies the PEP 440 and PEP 508 crates to pass CI, primarily by
fixing all lint violations.
We're also now using these crates in the workspace via `path`.
(Previously, we were still fetching them from Cargo.)
This PR copies over the `pep440-rs` crate at commit
`82aa5d4dcbe676b121dc931b0afa09a82de8e3d7` with no modifications.
It won't pass CI, but modifications will intentionally be confined to
later PRs.
