Sentry Issue: [POSTHOG-821](https://sentry.io/organizations/posthog/issues/3707400683/?referrer=github_integration)

Sentry is reporting that when listing session recordings loading persons is n+1

Looking at how the query works 

we 
* load person distinct ids for recordings in the list
* load the persons that have those distinct ids
* create a fict of distinct id to person
* for each of the recordings
    * look up the  person in the dict and pass them to a `PersonSerializer`
    * that looks up the person's distinct ids while choosing Person's `name`
    * (maybe only when there's no email) in order to determine the first distinct id for the person
    
 That final lookup of distinct ids is (**I think**) where the n plus 1 problem is. 
 
 For each person one at a time we go to the DB and get their distinct ids
 
 There's no foreign key from `Person` to `PersonDistinctId` so we can't utilise `select_related` here. 
 
 _maybe_ we can if we use a list serializer for Persons and then combine the two lists
 
 Some of the reports suggest 50% of the time generating the list is spent loading persons
posthog/api/test/test_session_recordings.py
with freeze_time("2020-09-13T12:26:40.000Z"):
            Person.objects.create(
                team=self.team, distinct_ids=["user"], properties={"$some_prop": "something", "email": "bob@bob.com"}
            )
            self.create_snapshot("user", "1", now() - relativedelta(days=1))
            self.create_snapshot("user", "2", now() - relativedelta(days=2))
            self.create_snapshot("user", "3", now() - relativedelta(days=3))
            
            params_string = urlencode({"session_ids": "[]"})
            response = self.client.get(f"/api/projects/{self.team.id}/session_recordings?{params_string}")
            self.assertEqual(response.status_code, status.HTTP_200_OK)
            response_data = response.json()
            self.assertEqual(len(response_data["results"]), 0)
    def test_regression_encoded_emojis_dont_crash(self):