Use designated initializers for Wayland listeners

[tarek-y-ismail]

It may be better to use designated initializers than rely on comments:

        .closed = [](

Originally posted by @AlanGriffiths in #377 (comment)

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Some tests don't use designated initializers when assigning handlers to events. Instead opting to use comments and the order of the handler declaration in the listener struct. It would be less error prone to use designated initializers directly.