Frame workboard empty/create states inside profile menu

Summary:
Ref T10054. Uncreated workboards feel a little awkward right now because you lose the menu. Instead, keep the menu.

I also plan to:

• add a "[X] Make the workboard the default view for this project." checkbox; and
• resolve T6961.

...which will touch this workflow, so modernize/straighten it out.

Test Plan:
Viewed workboard, no access state, empty state. Created empty board, imported board.

{F1066973}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T6961, T10054

Differential Revision: https://secure.phabricator.com/D15091