Enable extra build dependencies to 'match runtime' versions (#15036)

## Summary

This is an alternative to https://github.com/astral-sh/uv/pull/14944
that functions a little differently. Rather than adding separate
strategies, you can instead say:

```toml
[tool.uv.extra-build-dependencies]
child = [{ requirement = "anyio", match-runtime = true }]
```

Which will then enforce that `anyio` uses the same version as in the
lockfile.

crates/uv-build-frontend/src/lib.rs

@@ -328,6 +328,7 @@ impl SourceBuild {
             .and_then(|name| extra_build_requires.get(name).cloned())
             .unwrap_or_default()
             .into_iter()
+            .map(Requirement::from)
             .collect();
 
         // Create a virtual environment, or install into the shared environment if requested.