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.

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.: