[minor] Add CP4D uninstall support to MAS uninstall pipeline and CLI

[prajeshjain]

Summary

Adds Cloud Pak for Data (CP4D) uninstall capability to the MAS uninstall pipeline and CLI, enabling users to cleanly remove CP4D as part of a MAS dependency uninstall.

Changes

CLI (python/src/mas/cli/uninstall/)

• Added --uninstall-cp4d flag to the uninstall argument parser
• Added --cpd-operators-namespace and --cpd-instance-namespace arguments with sensible defaults
• Included CP4D in the --uninstall-all-deps shortcut path
• Added interactive prompt "Uninstall Cloud Pak for Data" in the guided uninstall flow
• Added CP4D parameters to the uninstall summary and pipeline submission

Tekton (tekton/)

• Added new task template tekton/src/tasks/dependencies/cp4d-uninstall.yml.j2 implementing the mas-devops-cp4d-uninstall Tekton Task, backed by the cp4d_uninstall Ansible role

• Registered cp4d-uninstall in generate-tekton-tasks.yml for automated task generation
• Added cp4d_action, cpd_operators_namespace, and cpd_instance_namespace pipeline parameters to mas-uninstall.yml.j2
• Wired in the uninstall-cp4d pipeline task to run in parallel with suite/app uninstall steps immediately after approval gate, conditioned on cp4d_action=uninstall

Notes

• The cp4d_uninstall Ansible role safely exits if CP4D is not installed, so enabling this is non-breaking
• CP4D uninstall runs in parallel with the suite uninstall for efficiency
• Namespace defaults (ibm-cpd-operators, ibm-cpd) are handled within the Ansible role when left blank