Fix app-namespace usage for cluster options

[praveenrewar]

What this PR does / why we need it:

During the introduction of defaultNamespace feature, we started using --app-namespace flag from kapp which should be used carefully when using cluster options instead of service account

The behaviour while using cluster options would be:

• If defaultNamespace is not used
  • kapp app and resources (if metadata.namespace is not provided) are created in cluster.Namespace if it is provided, or else the namespace from the kubeconfig is used.
• If defaultNamespace is provided
  • If cluster.Namespace is provided, then the kapp would be created there and the default namespace for the resources would be the defaultNamespace.
  • If clusterNamespace is not provided, then kapp app would be created in the kubeconfig namespace and the default namespace for the resources would be the defaultNamespace.

cluster.namespace	defaultNamespace	desired behaviour	PR behaviour
✅		meta: cluster.namespace, resources: cluster.namespace	Same as desired behaviour
✅	✅	meta: cluster.namespace, resources: defaultNamespace	Same as desired behaviour
	✅	meta: kubeconfig namespace, resources: defaultNamespace	Same as desired behaviour
		meta: kubeconfig namespace, meta: kubeconfig namespace	Same as desired behaviour

TODO

• Manual testing for the above scenarios.

Which issue(s) this PR fixes:

Fixes #1332

Does this PR introduce a user-facing change?

Additional Notes for your reviewer:

Review Checklist:

• Follows the developer guidelines
• Relevant tests are added or updated
• Relevant docs in this repo added or updated
• Relevant carvel.dev docs added or updated in a separate PR and there's
  a link to that PR
• Code is at least as readable and maintainable as it was before this
  change

Additional documentation e.g., Proposal, usage docs, etc.:

[neil-hickey]

LGTM, it's honestly quite confusing overall, not the PR but our general code flow because of all the scenarios. The tests nicely illustrate it, but the code is ... rough. Happy to refactor later on at some point.