Adds a flag to the insert layout action to explicitly set the focus of a
newly inserted node. This also adds a flag in the starter layout to
focus on the terminal block.
This adds a new NodeModel, which can be passed from the TileLayout to
contained blocks. It contains all the layout data that the block should
care about, including focus status, whether a drag operation is
underway, whether the node is magnified, etc.
This also adds a focus stack for the layout, which will let the focus
switch to the last-focused node when the currently-focused one is
closed.
This also addresses a regression in the resize handles that caused them
to be offset from the cursor when dragged.
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Co-authored-by: sawka <mike.sawka@gmail.com>
