Rationale: Sticky containers are always assigned to the visible
workspace.
The basic idea here is to check the destination's output (move.c:190).
But if the command was `move container to workspace x` then a workspace
might have been created for it. We could destroy the workspace in this
case, but that results in unnecessary IPC events.
To avoid this, the logic for `move container to workspace x` has been
adjusted. It now delays creating the workspace until the end, and uses
`workspace_get_initial_output` to determine and check the output before
creating it.
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