Persist multiple dashboards

[mattrunyon]

#1683 is to add support for displaying multiple dashboards. This issue will be for persisting multiple dashboards across page reloads. I've added a few TODOs with this issue number (Search "TODO: #1746") to spots where data should be stored/updated for dashboards, but it might not be comprehensive.

• Cleanup what is stored in workspaceData and migrate things like layoutConfig and links to dashboardData
• Persist dashboardData from redux (likely with a LocalDashboardStorage similar to LocalWorkspaceStorage)
• Properly rehydrate dh.ui dashboards
• Update import/reset layout to utilize dashboardData for the layout
• Consider porting over DashboardStorage from Enterprise