`workload tail` supports autocompletion for `--pod` values

[heyjcollins]

Description of problem

The pod names are frequently long and alphanumeric and typing in pod names is challenging to recall and error prone.

Proposed solution

When a user types tanzu apps workload tail my-app --pod + <TAB> the names of each of the pods associated with the my-app workload are displayed
When --pod flag/value has already been specified, autocomplete should only suggest pods which haven't already been specified in the command.

Describe alternatives you've considered

1. run workload get my-app
2. note the name of the pod you want to see the logs for
3. run kubectl logs pod/name-of-pod