watchNamespace to accept a list of namespaces to watch

**Is your feature request related to a problem?**
To allow the aws load balancer to watch multiple namespaces currently it accepts only one namespace

**Is your feature request related to a specific Helm chart, if yes mention name of the chart?**
yes, aws-load-balancer-controller

**Describe the solution you'd like**
To have this controller watch mulitple namespaces and work.

No error's are shown when multiple namespaces are also given makes it hard to see why the LBC is not working.

Start by inspecting the aws-load-balancer-controller Helm chart's watchNamespace configuration and how its rendered values reach the controller. Verify how multiple namespaces are represented and define completion as the controller watching and reconciling resources across all configured namespaces without silent failure.

Written by the indexing model from the issue text.