Move PackageCollectionProvider to async/await

Author: AndrewHoos

Sources/Basics/HTTPClient/LegacyHTTPClient.swift

@@ -307,6 +307,17 @@ public final class LegacyHTTPClient: Cancellable {
 }
 
 extension LegacyHTTPClient {
+    public func head(
+        _ url: URL,
+        headers: HTTPClientHeaders = .init(),
+        options: Request.Options = .init(),
+        observabilityScope: ObservabilityScope? = .none
+    ) async throws -> Response {
+        try await safe_async {
+            self.head(url, headers: headers, options: options, completion: $0)
+        }
+    }
+    @available(*, noasync, message: "Use the async alternative")
     public func head(
         _ url: URL,
         headers: HTTPClientHeaders = .init(),