## Bug description

Currently, decide endpoint takes 10+ seconds on kea.js.org.

This means that for first-time visitors autocapture nor session recording will be turned on for that long - losing valuable information.

When measuring this yesterday via shell ([slack thread](https://posthog.slack.com/archives/C0113360FFV/p1604951621008400)), the culprit was feature flags cohort checking. In this case, the cohort user was checked against was defined against the following action:

![Screenshot from 2020-11-10 11-41-32](https://user-images.githubusercontent.com/148820/98657215-49582e80-234a-11eb-9669-37d55e0d23bd.png)

Which currently looks through events of the data for that team.

## Expected behavior

Decide endpoint should use cached/materialized cohort ownership rather than calculating it on the fly.

## How to reproduce

1. Create an action with some selector
2. Create a cohort for has done action at any point
3. Create a feature flag using the cohort.
4. Measure /decide endpoint latency

## Environment

Cloud 

## Additional context

cc @EDsCODE who made it not time out by https://github.com/PostHog/posthog/pull/2299

#### *Thank you* for your bug report – we love squashing them!
ee/clickhouse/models/person.py
import datetime
import json
from typing import Any, Dict, List, Optional
from uuid import UUID, uuid4
from django.db.models.query import QuerySet
from django.db.models.signals import post_delete, post_save
from django.dispatch import receiver
from django.utils.timezone import now
from rest_framework import serializers
from ee.clickhouse.client import sync_execute
from ee.clickhouse.models.property import parse_prop_clauses
from ee.clickhouse.sql.person import (
    DELETE_PERSON_BY_ID,
    DELETE_PERSON_DISTINCT_ID_BY_PERSON_ID,
    DELETE_PERSON_EVENTS_BY_ID,
    GET_DISTINCT_IDS_SQL,
    GET_DISTINCT_IDS_SQL_BY_ID,
    GET_PERSON_BY_DISTINCT_ID,