Create and link a Priority label for a task imported from Phabricator

Phabricator tasks have an extended priority that looks like this when read from maniphest.search

        "priority": {
          "value": 100,
          "subpriority": 8588492800,
          "name": "Unbreak Now!",
          "color": "pink"
        },

We should find or create a project label with the name phab-priority::#{name} and link that to the issue.

When creating a label, we should prioritize it with the value from the JSON.