## Bug description

Support refreshing all dashboard items. This feature was temporarily removed because it wasn't working properly)

## Expected behavior
- All dashboard items should be properly refreshed and the `items` object in the `dashboardLogic` should contain the latest information.
- From user feedback. I expect items to be automatically refreshed every hour or so (e.g. if I'm a marketer that looks at graphs continuously during the day, or have a screen dedicated just to metrics).


## How to reproduce

1. Create a dashboard with multiple items
2. Attempt to refresh all and check the last refresh timestamp for each item (remember to uncomment relevant code)

## Environment

- [X] PostHog Cloud
- [X] self-hosted PostHog, version/commit: _please provide_

## Additional context
Follow-up to #3363

## Technical context

When refreshing all dashboard items (via `refreshAllDashboardItems()`) not all items are consistently refreshed all the time. Tested for instance with a dashboard with a couple of mixed (different type) graphs. Some items are still kept on "last refreshed 10 minutes ago".

In addition to the above, as originally reported on #3608, when calling `refreshAllDashboardItems` we update each item in their own scope, which means that the general `items` object in the upper scope logic (`dashboardLogic.js`) doesn't get updated. Not sure if we should propagate the change upwards, re-fetch everything, or just do a general refresh.

The UX problem this is causing is that the "Last refreshed" label now introduced in the dashboards gets outdated because `items` doesn't get updated. Having this object with outdated information also leads to other confusing UX issues.


#### *Thank you* for your bug report – we love squashing them!

posthog/api/dashboard.py
queryset = super().get_queryset().order_by("name")
        if self.action == "list":
            queryset = queryset.filter(deleted=False)
        queryset = queryset.prefetch_related(
            Prefetch("items", queryset=DashboardItem.objects.filter(deleted=False).order_by("order"),)
        )
        if self.request.GET.get("share_token"):
            return queryset.filter(share_token=self.request.GET["share_token"])
        elif self.request.user.is_authenticated and not self.request.user.team:
            raise NotFound()
        elif not self.request.user.is_authenticated or "team_id" not in self.get_parents_query_dict():
            raise AuthenticationFailed(detail="You're not logged in, but also not using add share_token.")
        return queryset
    def retrieve(self, request: Request, *args: Any, **kwargs: Any) -> response.Response:
        pk = kwargs["pk"]
        queryset = self.get_queryset()
        dashboard = get_object_or_404(queryset, pk=pk)
        dashboard.last_accessed_at = now()
        dashboard.save()
        serializer = DashboardSerializer(dashboard, context={"view": self, "request": request})
        return response.Response(serializer.data)
    def get_parents_query_dict(self) -> Dict[str, Any]:  
        if not self.request.user.is_authenticated or "share_token" in self.request.GET or not self.request.user.team:
            return {}
        return {"team_id": self.request.user.team.id}
class DashboardItemSerializer(serializers.ModelSerializer):