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

La issue non menziona file, test o punti di ingresso. Inizia individuando i percorsi esistenti per la creazione e l'aggiornamento dei cluster Spring Apps, quindi determina come viene rappresentata la ridondanza di zona e se è supportata una modifica in-place; il lavoro è completato quando può essere abilitata senza ricreare il cluster o ridistribuire i workload.

Scritto dal modello di indicizzazione a partire dal testo della issue.