Add support for HEAD requests in Maven registry (#21834) (#21929)

Backport of #21834

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

routers/web/repo/repo.go

@@ -426,7 +426,10 @@ func download(ctx *context.Context, archiveName string, archiver *repo_model.Rep
 	}
 	defer fr.Close()
 
-	ctx.ServeContent(downloadName, fr, archiver.CreatedUnix.AsLocalTime())
+	ctx.ServeContent(fr, &context.ServeHeaderOptions{
+		Filename:     downloadName,
+		LastModified: archiver.CreatedUnix.AsLocalTime(),
+	})
 }
 
 // InitiateDownload will enqueue an archival request, as needed.  It may submit