Add auto completion for flags

[rkpattnaik780]

Feature or problem description

CLI should have auto completion for flags wherever possible.

Proposed solution

Flags such as --output should be able to autocomplete themselves based on allowed values.

[craicoverflow]

Some more potential dynamic flags I have found:

rhoas kafka consumergroup list --topic <dynamic-value>
rhoas kafka create kafka-1 --provider <dynamic-value> --region <dynamic-value>

[craicoverflow]

Ah, I see you have already gotten to some of them @rkpattnaik780 :)