*** Code:
- ignore hidden tables and archived cards/dashboards
- correct docstring to indicate we are only getting 5 not 10 as
previously claimed
- in query, set limit to 8 in the case we get archived or non-existing
things and then take 5 in memory
- select extra properties from models that we need for this
determination

*** Tests:
- for mysql we were inserting views with a thread/sleep of one second
between each. Just compute timestamps seconds apart and do them all at
once. Should save 7 seconds off mysql test runs. verified temporal
spacing works with

```
 MB_DB_CONNECTION_URI="mysql://username:password@localhost:3306/cli" \
 clj -X:dev:test :only metabase.api.activity-test
```
- cleanup these activities we were creating with `mt/with-model-cleanup`
which introduces a big looking diff. But checking diff with whitespace
shows its just an indentation and then add the extra keys needed for
identifying which are archived (:archived and :visibility_type for cards
and tables respectively)