## 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
import json
from datetime import datetime
from typing import Dict, List, Optional, Tuple, Union
from unittest.mock import patch
from django.conf import settings
from django.core.cache import cache
from django.utils import timezone
from freezegun import freeze_time
from rest_framework.exceptions import ValidationError
from posthog.constants import (
    ENTITY_ID,
    ENTITY_TYPE,
    TREND_FILTER_TYPE_EVENTS,
    TRENDS_BAR_VALUE,
    TRENDS_LINEAR,
    TRENDS_TABLE,
)
from posthog.models import (
    Action,
    ActionStep,
    Cohort,
    Entity,
    Filter,
    GroupTypeMapping,
    Organization,
    Person,
)
from posthog.models.group.util import create_group