kubectl-oadp CLI Plugin Implementation (OADP-6544)

The kubectl-oadp CLI Plugin Implementation (OADP-6544) is an ongoing project aimed at providing a kubectl-native interface for OADP operations. This extension will integrate kubectl with existing oadp-cli functionality, enhancing usability. However, the progress is currently stalled due to several dependent tasks, including setting user credentials, supporting namespace with -n flag, help documentation, and various other development tasks. The successful completion of this epic is crucial for the OADP 1.6.0 release (OADP-6580), which is planned for OpenShift 4.22 or later. The design document can be found at https://github.com/migtools/oadp-cli/blob/main/design/kubectl-oadp-design.md.