The ListParameter.parent property only existed to make the deserialier's
life easier, but is also why sketchy code was needed for appending search
criteria from a ServerSearchEmail replay op to the actual IMAP search
command sent to the server.
This removes the property altogether, and replaces its only use in
Deserialier with a stack, as nature intended. This means lists can be
added to more than one other list, and e.g. when a search is executed,
the search critera can be used for multiple requests.
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