Application namespaces should be created only by the controller since the ApplicationGroup owns each of the created resources

[nitishm]

Currently, the namespace creation is duplicated in both the reconciler and the executor container. It would be better to have the reconciler create the namespace while ignoring 'Already Exists' errors.

Additionally, in keeping with helm client's --create-namespace option, the created namespace should also be labeled with

labels:
  name: <namespace>

[nitishm]

/cc @jonathan-innis @mgl1969

[nitishm]

For reference, the two places where this happens currently are,

Orkestra:
https://github.com/Azure/orkestra/blob/main/pkg/workflow/argo.go#L121-L133

Workflow Executor:
https://github.com/Azure/orkestra-workflow-executor/blob/main/main.go#L116-L136