If pin-tags is set, there is no format defined for tags that are not occupied.
However defining a format for unoccupied tags makes the pin-tags setting
redundant since then the label can just be set to empty to not show unoccupied
tags.
Following the above reasoning, the pin tags setting is removed, and
state_t::NONE is renamed to state_t::EMPTY. This way if a user wants to display
empty tags, they can specify the format, otherwise they can simply set the label
to an empty string.
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