Include must-gather in the oadp-cli

[mpryc]

It woud be cool to add must-gather as part of the subcommand of this CLI mosty for admin cases.

[Joeavaikath]

https://docs.okd.io/latest/backup_and_restore/application_backup_and_restore/troubleshooting/using-the-must-gather-tool.html

[Joeavaikath]

must-gather is version specific
oadp-cli user needs to run must-gather, they run a cli command to trigger it
where should it trigger from