Implement a rough optgroup-based "Move on Workboard" stacked action

Summary:
Ref T6027. Try this out and see how it feels? Clear issues:

• This definitely shouldn't be at the top.
• You should probably be able to select it multiple times?
• Some of the "which columns show up" rules might need adjustment?
• Diamond marker maybe not great?

Not sure I love this but it doesn't feel terrible...

Test Plan: {F1207891}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T6027

Differential Revision: https://secure.phabricator.com/D15638