💡 Feature Request - Support Dynamic Outbound Rule Creation During Migration

## Describe the solution you'd like

Because outbound rules can only associate a single backend pool to a single front end IP address, in the situation where an external load balancer has multiple backend pools, we are not able to create a generic outbound rule that applies to all backend pool members. Currently, the module issues a warning and instructs user to manually configure outbound rules post migration.

Potential solutions:
- Distribute outbound rule allocated outbound ports across each backend pool (creating an outbound rule for each backend pool)
- Allow user to create a new backend pool with the members from all of the LB's original backend pools; create an outbound rule associating this backend pool to the first front end IP
- Allow user to map existing backend pools to front end IPs

## Describe alternatives you've considered

Current state warns user to create outbound rules post migration.

## Additional context

See #10

issue #10 と、アウトバウンドルールを手動で設定するよう警告を出す現在の移行経路をレビューする。提案されている backend-pool と frontend-IP の動作のうち、どれを実装すべきかを明確にし、その後、移行によって複数の backend pool に対する適切なアウトバウンドルールが作成され、移行後の設定が不要になることを確認する。

索引モデルが issue の本文から書いたものです。