Add task creation support

[burmanm]

There is already a lot of code for creating tasks in k8ssandra-client, but there's no corresponding cmd util to use them from the CLI. We should add all the methods under

tasks create <method>.

As well as tasks list to show all the tasks that have been executed (or are executing - depending on the parameters given to the command).

┆Issue is synchronized with this Jira Task by Unito
┆Issue Number: K8CL-3