test: kubectl-dns secret-generation command

[averevki]

Description

• Add support for kubectl-dns CLI tool integration to the test suite
• Implement wrapper class and test for the kubectl-dns secret-generation command
• Refactor CLI tooling by moving kuadrantctl into a dedicated testsuite/cli/ module

Verification steps

Run the new test:

poetry run pytest -vv testsuite/tests/multicluster/coredns/two_clusters/kubectl-dns/test_secret_generation.py

Note: This test requires:

• The kubectl-dns binary to be available in PATH or configured in config/settings.local.yaml
• A multicluster CoreDNS setup with one primary and one secondary cluster
• 2 kubeconfigs containing certificate-authority key with the cluster CA. You can set it for a kubeconfig by logging in with explicitly specified path to the cluster CA, aka. oc login --username=${} --password=${} <clusterapiurl> --certificate-authority=path/to/ca