Ref T13591. Add more selector flags to let "bin/worker" commands operate on tasks by container PHID, object PHID, priority, etc.

This anticipates adding "bin/worker reprioritize" and "bin/worker delay" workflows, to provide more tools for handling repository imports.

• Ran bin/worker execute, cancel, retry, and free with various sets of selector flags.
• Used --min-priority, --max-priority, --object, --container, --archived, --max-failure-count to select tasks.
• Specified invalid, duplicate, aliased objects with "--object".
• Specified invalid range priority selectors.