Allow conflicting Git URLs that refer to the same commit SHA (#2769)

## Summary

This PR leverages our lookahead direct URL resolution to significantly
improve the range of Git URLs that we can accept (e.g., if a user
provides the same requirement, once as a direct dependency, and once as
a tag). We did some of this in #2285, but the solution here is more
general and works for arbitrary transitive URLs.

Closes https://github.com/astral-sh/uv/issues/2614.

crates/cache-key/src/canonical_url.rs

@@ -91,6 +91,12 @@ impl Hash for CanonicalUrl {
     }
 }
 
+impl From<CanonicalUrl> for Url {
+    fn from(value: CanonicalUrl) -> Self {
+        value.0
+    }
+}
+
 impl std::fmt::Display for CanonicalUrl {
     fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
         std::fmt::Display::fmt(&self.0, f)