Unlike nonPriorityDebounced, if one of priorityDebounced
or priorityUnfiltered are
called while the future is in progress, the FutureWidget will
display the value for a short amount of time, before being replaced by
the value/exception emitted by later invoked, completed future.
"Unfiltered" indicates the absence of such a filtering process.
It has higher priority than non-priority refreshes.
This option allows immediate rebuilds in quick succession: it doesn't
debounce the refreshes; instead, it triggers a rebuild
immediately after a refresh is requested.