## 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
"""
GET_LATEST_PERSON_ID_SQL = """
(select id from (
    {latest_person_sql}
))
""".format(
    latest_person_sql=GET_LATEST_PERSON_SQL
)
GET_PERSON_SQL = """
SELECT * FROM ({latest_person_sql}) person WHERE team_id = %(team_id)s
""".format(
    latest_person_sql=GET_LATEST_PERSON_SQL
)
PERSONS_DISTINCT_ID_TABLE = "person_distinct_id"
PERSONS_DISTINCT_ID_TABLE_BASE_SQL = """
CREATE TABLE {table_name} 
(
    id Int64,
    distinct_id VARCHAR,
    person_id UUID,
    team_id Int64
    {extra_fields}
) ENGINE = {engine} 
"""
PERSONS_DISTINCT_ID_TABLE_SQL = (
    PERSONS_DISTINCT_ID_TABLE_BASE_SQL
    + """Order By (team_id, distinct_id, person_id, id)
{storage_policy}
"""
).format(