Improve sorting mini-tree results

[sifnoc]

While collecting min-tree from executors, the Orchestrator has a logic that copies and sorts processed task for returning result.
but it’s too time consuming.

summa-aggregation/src/orchestrator/mod.rs

Lines 224 to 234 in 7dba825

	let all_tree_results = join_all(all_tree_responses).await;
	// Aggregate results from all workers in order
	let mut ordered_tree_results = vec![None; self.entry_csvs.len()];
	for result in all_tree_results {
	let (index, worker_results) = result.unwrap();
	let start = index * entries_per_executor;
	for (i, res) in worker_results.iter().enumerate() {
	ordered_tree_results[start + i] = Some(res.clone());
	}
	}

We can improve this part use rayon