This adds a 3 second timeout to the initial reply in swaymsg. This
prevents swaymsg from hanging when `swaymsg -t get_{inputs,seats}` is
used in i3. The timeout is removed when waiting for a subscribed event
or monitoring for subscribed events.
This also adds type checks to commands where i3 does not reply with all
of the properties that sway does (such as `modes` in `get_outputs`).
This is mostly just a behavioral adjustment since swaymsg should run on
i3. When running under i3, some command reply's (such as the one for
`get_outputs) may have more useful information in the raw json than the
pretty printed version.
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