chore: Move all integration tests to a single binary (#8093)

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).

crates/uv-macros/Cargo.toml

@@ -5,6 +5,7 @@ edition = "2021"
 
 [lib]
 proc-macro = true
+doctest = false
 
 [lints]
 workspace = true