Workspaces previously had a magical `workspace->floating` container,
which had a layout of L_FLOATING and whose children were actual floating
views. This allowed some conveniences, but was a hacky solution because
the container has to be exempt from focus, coordinate transactions with
the workspace, and omit emitting IPC events (which we didn't do).
This commit changes it to be a list directly in the sway_workspace. The
L_FLOATING layout is no longer used so this has been removed as well.
* Fixes incorrect check in the swap command (it checked if the
containers had the L_FLOATING layout, but this layout applied to the
magical container).
* Introduces workspace_add_floating
This creates a root.c and moves bits and pieces from elsewhere into it.
* layout_init has been renamed to root_create and moved into root.c
* root_destroy has been created and is called on shutdown
* scratchpad code has been moved into root.c, because hidden scratchpad
containers are stored in the root struct
Implements the following commands:
* move scratchpad
* scratchpad show
* [criteria] scratchpad show
Also fixes these:
* Fix memory leak when executing command with criteria
(use `list_free(views)` instead of `free(views)`)
* Fix crash when running `move to` with no further arguments
