Refactor packages (func name & UI) (#34773)

1. Use `OpenXxx` instead of `GetXxx` because the returned readers should
be correctly closed, and clarify the behaviors of the functions: they
increase the download counter
2. Use `packages-content` styles instead of `issue-content`

routers/api/packages/helm/helm.go

@@ -122,7 +122,7 @@ func DownloadPackageFile(ctx *context.Context) {
 		return
 	}
 
-	s, u, pf, err := packages_service.GetFileStreamByPackageVersion(
+	s, u, pf, err := packages_service.OpenFileForDownloadByPackageVersion(
 		ctx,
 		pvs[0],
 		&packages_service.PackageFileInfo{