uv-resolver: use named fields for some PubGrubPackage variants

I'm planning to add another field here (markers), which puts a lot of
stress on the positional approach. So let's just switch over to named
fields.

crates/uv-resolver/src/resolver/batch_prefetch.rs

@@ -53,7 +53,12 @@ impl BatchPrefetcher {
         index: &InMemoryIndex,
         selector: &CandidateSelector,
     ) -> anyhow::Result<(), ResolveError> {
-        let PubGrubPackage::Package(package_name, None, None) = &next else {
+        let PubGrubPackage::Package {
+            name,
+            extra: None,
+            url: None,
+        } = &next
+        else {
             return Ok(());
         };
 
@@ -66,7 +71,7 @@ impl BatchPrefetcher {
         // This is immediate, we already fetched the version map.
         let versions_response = index
             .packages()
-            .wait_blocking(package_name)
+            .wait_blocking(name)
             .ok_or(ResolveError::Unregistered)?;
 
         let VersionsResponse::Found(ref version_map) = *versions_response else {
@@ -85,7 +90,7 @@ impl BatchPrefetcher {
                     previous,
                 } => {
                     if let Some(candidate) =
-                        selector.select_no_preference(package_name, &compatible, version_map)
+                        selector.select_no_preference(name, &compatible, version_map)
                     {
                         let compatible = compatible.intersection(
                             &Range::singleton(candidate.version().clone()).complement(),
@@ -103,13 +108,13 @@ impl BatchPrefetcher {
                     }
                 }
                 BatchPrefetchStrategy::InOrder { previous } => {
-                    let range = if selector.use_highest_version(package_name) {
+                    let range = if selector.use_highest_version(name) {
                         Range::strictly_lower_than(previous)
                     } else {
                         Range::strictly_higher_than(previous)
                     };
                     if let Some(candidate) =
-                        selector.select_no_preference(package_name, &range, version_map)
+                        selector.select_no_preference(name, &range, version_map)
                     {
                         phase = BatchPrefetchStrategy::InOrder {
                             previous: candidate.version().clone(),
@@ -148,7 +153,7 @@ impl BatchPrefetcher {
             }
         }
 
-        debug!("Prefetching {prefetch_count} {package_name} versions");
+        debug!("Prefetching {prefetch_count} {name} versions");
 
         self.last_prefetch.insert(next.clone(), num_tried);
         Ok(())
@@ -157,7 +162,7 @@ impl BatchPrefetcher {
     /// Each time we tried a version for a package, we register that here.
     pub(crate) fn version_tried(&mut self, package: PubGrubPackage) {
         // Only track base packages, no virtual packages from extras.
-        if matches!(package, PubGrubPackage::Package(_, Some(_), _)) {
+        if matches!(package, PubGrubPackage::Package { extra: Some(_), .. }) {
             return;
         }
         *self.tried_versions.entry(package).or_default() += 1;