Following a CI failure in https://github.com/astral-sh/uv/pull/15028,
ensure that all workspace crates are inheriting the MSRV and other
workspace configuration from the workspace root.
## Summary
Resolves#8417
I've just begun learning procedural macros, so this PR is more of a
proof of concept. It's still a work in progress, and I welcome any
assistance or feedback.
As per
https://matklad.github.io/2021/02/27/delete-cargo-integration-tests.html
Before that, there were 91 separate integration tests binary.
(As discussed on Discord — I've done the `uv` crate, there's still a few
more commits coming before this is mergeable, and I want to see how it
performs in CI and locally).
