feat: add script to resync person on events for a team

[tiina303]

Problem

Not fully ready yet, but wanted to make sure we agree on the approach:

1. since we might need to run it more in the future - adding it as a management command to our django shell instead of a random script somewhere
2. to populate the initial tables looked used select instead of what the migration did as I suspect that's a lot faster if we're talking about a single team.

Changes

👉 Stay up-to-date with PostHog coding conventions for a smoother review.

How did you test this code?

Tested locally by creating some persons and aliasing them - saw that the person_ids were updated after running the cmd

posthog.capture('test-id-2022-09-20-15-58', 'test-event-2022-09-20-15-58')
posthog.capture('test-id-2022-09-20-15-59', 'test-event-2022-09-20-15-59')
posthog.alias('test-id-2022-09-20-15-58', 'test-id-2022-09-20-15-59')  # after waiting

resulted in local CH

select event, person_id from events where team_id=3

| event                        | person_id
|------------------------------|-----------------
│ $create_alias                │ 01835b33-63fe-0000-91cc-2c4387db354b
│ test-event-2022-09-20-15-58  │ 01835b33-63fe-0000-91cc-2c4387db354b
│ test-event-2022-09-20-15-59  │ 01835b33-9b5a-0000-adc4-61a873a3c7e8

Then (also tested other steps separately)

DEBUG=1 python manage.py resync_persons_on_events --team-id 3 --live-run

resulted in local CH

select event, person_id from events where team_id=3

| event                        | person_id
|------------------------------|-----------------
│ $create_alias                │ 01835b33-63fe-0000-91cc-2c4387db354b
│ test-event-2022-09-20-15-58  │ 01835b33-63fe-0000-91cc-2c4387db354b
│ test-event-2022-09-20-15-59  │ 01835b33-63fe-0000-91cc-2c4387db354b