Make turning on zone redundancy an 'in place' change

**Is your feature request related to a problem? Please describe.**

Currently when you want to enable zone redundancy for an existing Spring Apps cluster, this can't be done 'in place', instead the full cluster needs to be recreated and all workloads need to be redeployed on the new cluster.

**Describe the solution you'd like**

It would be much more beneficial if the zone redundancy were a switch you can just enable on an existing cluster.

**Describe alternatives you've considered**

NA

**Describe the Customer Impact**

I see customers having issues with resilience and often it's because they did not use the zone redundancy feature during cluster creation. They are already far in using the cluster for multiple workloads. Turning on zone redundancy now is not possible on their existing cluster, which makes it a difficult process to increase their overall resilience, with potential downtime as a result.

**Additional context**

NA

**Can we contact you for additional details?** Y/N

Y

この issue にはファイル、テスト、エントリーポイントが記載されていません。まず既存の Spring Apps クラスターの作成および更新パスを特定し、次にゾーン冗長性がどのように表現されているか、インプレースでの変更がサポートされているかを確認してください。クラスターを再作成したりワークロードを再デプロイしたりせずに有効化できれば完了です。

索引モデルが issue の本文から書いたものです。