Move per-minion telegraf cred provisioning into so-minion

Simpler, race-free replacement for the reactor + orch + fan-out chain.

- salt/manager/tools/sbin/so-minion: expand add_telegraf_to_minion to
  generate a random 72-char password, reuse any existing password from
  the aggregate pillar, write postgres.telegraf.{user,pass} into the
  minion's own pillar file, and update the aggregate pillar so
  postgres.telegraf_users can CREATE ROLE on the next manager apply.
  Every create<ROLE> function already calls this hook, so add / addVM /
  setup dispatches are all covered identically and synchronously.
- salt/postgres/auth.sls: strip the fanout_targets loop and the
  postgres_telegraf_minion_pillar_<safe> cmd.run block — it's now
  redundant. The state still manages the so_postgres admin user and
  writes the aggregate pillar for postgres.telegraf_users to consume.
- salt/reactor/telegraf_user_sync.sls: deleted.
- salt/orch/telegraf_postgres_sync.sls: deleted.
- salt/salt/master.sls: drop the reactor_config_telegraf block that
  registered the reactor on /etc/salt/master.d/reactor_telegraf.conf.
- salt/orch/deploy_newnode.sls: drop the manager_fanout_postgres_telegraf
  step and the require: it added to the newnode highstate. Back to its
  original 3/dev shape.

No more ephemeral postgres_fanout_minion pillar, no more async salt/key
reactor, no more so-minion setupMinionFiles race: the pillar write
happens inline inside setupMinionFiles itself.

salt/reactor/telegraf_user_sync.sls

@@ -1,18 +0,0 @@
-# Copyright Security Onion Solutions LLC and/or licensed to Security Onion Solutions LLC under one
-# or more contributor license agreements. Licensed under the Elastic License 2.0 as shown at
-# https://securityonion.net/license; you may not use this file except in compliance with the
-# Elastic License 2.0.
-
-{# Fires on salt/key. Only act on successful key acceptance — not reauth. #}
-{% if data.get('act') == 'accept' and data.get('result') == True and data.get('id') %}
-
-{{ data['id'] }}_telegraf_pg_sync:
-  runner.state.orchestrate:
-    - args:
-      - mods: orch.telegraf_postgres_sync
-      - pillar:
-          postgres_fanout_minion: {{ data['id'] }}
-
-{% do salt.log.info('telegraf_user_sync reactor: syncing telegraf PG user for minion %s' % data['id']) %}
-
-{% endif %}