## 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/sql/person.py
where person_distinct_id.team_id = %(team_id)s
"""
INSERT_PERSON_SQL = """
INSERT INTO person SELECT %(id)s, %(created_at)s, %(team_id)s, %(properties)s, %(is_identified)s, now(), 0
"""
INSERT_PERSON_DISTINCT_ID = """
INSERT INTO person_distinct_id SELECT %(id)s, %(distinct_id)s, %(person_id)s, %(team_id)s, now(), 0 VALUES
"""
UPDATE_PERSON_PROPERTIES = """
ALTER TABLE person UPDATE properties = %(properties)s where id = %(id)s
"""
UPDATE_PERSON_ATTACHED_DISTINCT_ID = """
ALTER TABLE person_distinct_id UPDATE person_id = %(person_id)s where distinct_id = %(distinct_id)s
"""
DELETE_PERSON_BY_ID = """
ALTER TABLE person DELETE where id = %(id)s
"""
DELETE_PERSON_EVENTS_BY_ID = """
ALTER TABLE events DELETE
where distinct_id IN (
    SELECT distinct_id FROM person_distinct_id WHERE person_id=%(id)s AND team_id = %(team_id)s
)
AND team_id = %(team_id)s
"""
DELETE_PERSON_DISTINCT_ID_BY_PERSON_ID = """
ALTER TABLE person_distinct_id DELETE where person_id = %(id)s
"""
UPDATE_PERSON_IS_IDENTIFIED = """
ALTER TABLE person UPDATE is_identified = %(is_identified)s where id = %(id)s
"""