Give internal API user admin permission on all silos

[leftwo]

This updates the built in user USER_INTERNAL_API to have admin permissions on all silos.

A new constant, USER_INTERNAL_API was added to the PolarClass and a new entry in the
polar config file was added for this user.

Also, the saga_id was added to the logs to assist in tracking a sagas actions through the
authz logs:

{
  "msg": "authorize result",
  "v": 0,
  "name": "9ee34684-9643-4cce-b3af-f7b8825042ea",
  "level": 20,
  "time": "2022-09-13T23:44:08.460180604Z",
  "hostname": "atrium",
  "pid": 10225,
  "saga_node": "FinalizeDiskRecord",
  "actor_id": "001de000-05e4-4000-8000-000000004007",
  "authenticated": true,
  "saga_id": "976b0315-cf99-4d17-bbeb-d5c4e9c2fa55",
  "saga_name": "disk-create",
  "component": "ServerContext",
  "result": "Ok(())",
  "resource": "Database",
  "action": "Query",
  "actor": "Some(Actor::SiloUser { silo_user_id: 001de000-05e4-4000-8000-000000004007, silo_id: 001de000-5110-4000-8000-000000000000, .. })"
}

[davepacheco]

Context for the record: recall that we don't have a plan for internal authz. So when I initially added the "internal API" user, I granted them all privileges by creating a built-in role assignment that grants this user the "fleet admin" role on the sole fleet. After #1580, this no longer granted superuser privileges. This change restores that previous behavior.

Longer term, of course we ought to have a plan for more restricted authz on the internal API.

[leftwo]

Thanks @davepacheco for the extensive help for these changes.