Fix home regeneration (#6251)

* Fix regeneration marker not being removed after completion

* Return HTTP 206 from /api/v1/timelines/home if regeneration in progress
Prioritize RegenerationWorker by putting it into default queue

* Display loading indicator and poll home timeline while it regenerates

* Add graphic to regeneration message

* Make "not found" indicator consistent with home regeneration

app/javascript/mastodon/features/ui/containers/status_list_container.js

@@ -47,6 +47,7 @@ const makeMapStateToProps = () => {
   const mapStateToProps = (state, { timelineId }) => ({
     statusIds: getStatusIds(state, { type: timelineId }),
     isLoading: state.getIn(['timelines', timelineId, 'isLoading'], true),
+    isPartial: state.getIn(['timelines', timelineId, 'isPartial'], false),
     hasMore: !!state.getIn(['timelines', timelineId, 'next']),
   });