## Bug description

When calculating Trends results with an aggregated (e.g. single output, like big number) display type, WAU/MAU don't work. This is because we have an `ACTIVE_USERS_SQL` query for time series display types, but we don't have a version of this for aggregated display types. (See ZEN-1043.)

## How to reproduce

1. Create an insight with a single WAU or MAU series.
2. Switch display type to "Number".
3. Open the "Debug ClickHouse queries" modal from the command palette.
4. See `COUNT(*)` instead of `COUNT(DISTINCT person_id)`.

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posthog/queries/test/test_trends.py
{"key": "industry", "value": "finance", "type": "group", "group_type_index": 0},
                    {"key": "key", "value": "value", "type": "person"},
                ],
            },
            team=self.team,
        )
        with override_instance_config("PERSON_ON_EVENTS_ENABLED", True):
            response = Trends().run(filter, self.team)
            self.assertEqual(response[0]["count"], 1)
    @test_with_materialized_columns(
        group_properties=[(0, "industry"), (2, "name")], materialize_only_with_person_on_events=True
    )
    @snapshot_clickhouse_queries
    def test_filtering_by_multiple_groups_person_on_events(self):
        GroupTypeMapping.objects.create(team=self.team, group_type="organization", group_type_index=0)
        GroupTypeMapping.objects.create(team=self.team, group_type="company", group_type_index=2)
        create_group(team_id=self.team.pk, group_type_index=0, group_key="org:5", properties={"industry": "finance"})
        create_group(team_id=self.team.pk, group_type_index=0, group_key="org:6", properties={"industry": "technology"})
        create_group(team_id=self.team.pk, group_type_index=2, group_key="company:5", properties={"name": "five"})
        create_group(team_id=self.team.pk, group_type_index=2, group_key="company:6", properties={"name": "six"})
        journey = {
            "person1": [
                {
                    "event": "sign up",
                    "timestamp": datetime(2020, 1, 2, 12),
                    "properties": {"$group_0": "org:5", "$group_2": "company:6"},
                },
                {
                    "event": "sign up",
                    "timestamp": datetime(2020, 1, 2, 12, 30),