## 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The UX problem this is causing is that the "Last refreshed" label now introduced in the dashboards gets outdated because `items` doesn't get updated. Having this object with outdated information also leads to other confusing UX issues.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
request = self.context["request"]
        validated_data["created_by"] = request.user
        team = Team.objects.get(id=self.context["team_id"])
        use_template: str = validated_data.pop("use_template", None)
        creation_mode = "template" if use_template else "default"
        dashboard = Dashboard.objects.create(team=team, creation_mode=creation_mode, **validated_data)
        if use_template:
            try:
                create_dashboard_from_template(use_template, dashboard)
            except AttributeError:
                raise serializers.ValidationError({"use_template": "Invalid value provided."})
        elif request.data.get("items"):
            for item in request.data["items"]:
                DashboardItem.objects.create(
                    **{key: value for key, value in item.items() if key not in ("id", "deleted", "dashboard", "team")},
                    dashboard=dashboard,
                    team=team,
                )
        posthoganalytics.capture(
            request.user.distinct_id,
            "dashboard created",
            {**dashboard.get_analytics_metadata(), "from_template": bool(use_template), "template_key": use_template},
        )
        return dashboard
    def update(self, instance: Dashboard, validated_data: Dict, *args: Any, **kwargs: Any,) -> Dashboard: