`org_type` already exists as a field in the Realm model and is
used when organizations are created / updated in Zulip Cloud,
via the `/analytics/support` view.
Extends the `PATCH /realm` view to be able update `org_type` as
other realm / organization settings are updated, but using the
special log / action that was created for the analytics view.
Adds a field to the `realm op: update` / `realm op: update_dict`
events, which also means an event is now sent when and if the
`org_type` is updated via the analytics view. This is similar
to how updates to an organization's `plan_type` trigger events.
Adds `realm_org_type` as a realm setting fetched from the
`POST /register` endpoint.
Based on an audit, this closes out the last core instances in which
acting_user was not being passed explicitly when creating
RealmAuditLog instances.
There are some outstanding issues in the billing system, which we plan
to extract as a separate issue.
Fixes#14808.