Preserve .git suffixes and casing in Git dependencies (#2789)

## Summary

I noticed in #2769 that I was now stripping `.git` suffixes from Git
URLs after resolving to a precise commit. This PR cleans up the internal
caching to use a better canonical representation: a `RepositoryUrl`
along with a `GitReference`, instead of a `GitUrl` which can contain
non-canonical data. This gives us both better fidelity (preserving the
`.git`, along with any casing that the user provided when defining the
URL) and is overall cleaner and more robust.

crates/cache-key/src/canonical_url.rs

@@ -165,6 +165,12 @@ impl Deref for RepositoryUrl {
     }
 }
 
+impl std::fmt::Display for RepositoryUrl {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        std::fmt::Display::fmt(&self.0, f)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;