fix: Person properties updates to update op and ts too

[tiina303]

Problem

EDIT: latest discussion: https://posthog.slack.com/archives/C0374DA782U/p1660840149534569

Closes https://github.com/PostHog/posthog/issues/10661

We have last updated at and last operation for debugging among other reasons, however they weren't correct.

If we send events to update the person properties, then last operation and last timestamp aren't updated properly specifically sending these events:

posthog.capture('test-ts-op', 'test-event', properties={'$set':{'p1':'tretwdw', 'p2': 'trwhrts' }})
posthog.capture('test-ts-op', 'test-event', properties={'$set':{'p1':'new', 'p3': 'nnn' }})

Before this PR

Notice how last op and last updated ts didn't get updated with the second event

select * from posthog_person where id=7;
 id |         created_at         |                 properties                  | team_id | is_user_id | is_identified |                 uuid                 |                      properties_last_updated_at                      | properties_last_operation  | version
----+----------------------------+---------------------------------------------+---------+------------+---------------+--------------------------------------+----------------------------------------------------------------------+----------------------------+---------
  7 | 2022-08-17 14:22:05.103+00 | {"p1": "new", "p2": "trwhrts", "p3": "nnn"} |       1 |            | f             | 0182ac2f-bfc9-0000-01f9-de3abab094f5 | {"p1": "2022-08-17T14:22:05.103Z", "p2": "2022-08-17T14:22:05.103Z"} | {"p1": "set", "p2": "set"} |       1

After this PR

select * from posthog_person where id=8;
 id |         created_at         |                 properties                  | team_id | is_user_id | is_identified |                 uuid                 |                                       properties_last_updated_at                                       |        properties_last_operation        | version
----+----------------------------+---------------------------------------------+---------+------------+---------------+--------------------------------------+--------------------------------------------------------------------------------------------------------+-----------------------------------------+---------
  8 | 2022-08-17 14:29:21.547+00 | {"p1": "new", "p2": "trwhrts", "p3": "nnn"} |       1 |            | f             | 0182ac36-6737-0000-073f-9ad95542ac67 | {"p1": "2022-08-17T14:30:59.446Z", "p2": "2022-08-17T14:29:21.547Z", "p3": "2022-08-17T14:30:59.446Z"} | {"p1": "set", "p2": "set", "p3": "set"} |       1

Changes

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

Also updated person-state to not have a .only test

How did you test this code?

See above in problem statement.