Get pending task info from funcX CLI

When debugging endpoint issues, it would be really convenient to be able to see pending task statuses for an active endpoint. For example, `funcx-endpoint tasks ` could return each task that is currently running on the endpoint and optionally a log of recently completed tasks

Start by locating the funcX CLI's endpoint command entry points and the existing endpoint task-status handling. Confirm how the command should report currently running tasks and whether a log of recently completed tasks is required; the issue is done when that behavior is defined and exposed through the proposed endpoint command.

Written by the indexing model from the issue text.