Allow for field and label selectors use in commands

Current situation

Issue orchestrator#333 (closed) allowing for filter (i.e. field and label selectors) use in observer /channels and /workflows/{workflow_id}/status endpoints, we need to provide the possibility to use filters within opentf-ctl ... commands.

Desired outcome

opentf-ctl ... commands that adress these endpoints must allow for field and label selectors use to filter the output results.

To preserve compatibility with our current usage of (label) selectors for the get namespaces command and to keep familiarity for kubectl users, we will use the following:

• --selector (or -l) for label selectors
• --field-selector for field selectors