## Is your feature request related to a problem?

As a team accumulates data, they will have events/properties that are no longer in use that clutter their app.

Example from our team:
![image](https://user-images.githubusercontent.com/148820/143202334-42d73ab6-13be-4661-ba7a-83c86788b9e8.png)


## Describe the solution you'd like

Under event/properties stats allow 'hiding' events/properties from view.

## Describe alternatives you've considered

Alternatively, go the route of "verified" events/properties (as He@p) does - show those first. See also https://help.heap.io/category/heap-administration/data-governance/

## Additional context

Note: Existing reports, etc should still work well even with 'removed' events/properties.

Related: https://github.com/PostHog/posthog/issues/7126

#### *Thank you* for your feature request – we love each and every one!

posthog/api/property_definition.py
query = f"""
            SELECT {self.property_definition_fields}, {self.event_property_field} AS is_seen_on_filtered_events
            FROM {self.table}
            {self._join_on_event_property()}
            WHERE posthog_propertydefinition.team_id = %(team_id)s
              AND type = %(type)s
              AND coalesce(group_type_index, -1) = %(group_type_index)s
              {self.excluded_properties_filter}
             {self.name_filter} {self.numerical_filter} {self.search_query} {self.event_property_filter} {self.is_feature_flag_filter}
             {self.event_name_filter}
            ORDER BY is_seen_on_filtered_events DESC, posthog_propertydefinition.query_usage_30_day DESC NULLS LAST, posthog_propertydefinition.name ASC
            LIMIT {self.limit} OFFSET {self.offset}
            """
        return query
    def as_count_sql(self):
        query = f"""
            SELECT count(*) as full_count
            FROM {self.table}
            {self._join_on_event_property()}
            WHERE posthog_propertydefinition.team_id = %(team_id)s
              AND type = %(type)s
              AND coalesce(group_type_index, -1) = %(group_type_index)s
             {self.excluded_properties_filter} {self.name_filter} {self.numerical_filter} {self.search_query} {self.event_property_filter} {self.is_feature_flag_filter}
             {self.event_name_filter}
            """
        return query
    def _join_on_event_property(self):
        return (