fix(mqtt-bridge): disallow QoS 2 on ingress bridges

[keynslug]

Also bring back the ability to configure clean_start, but only for subscriptions to the ingresses.

---

EMQX-8934

[coveralls]

Pull Request Test Coverage Report for Build 4145674796

• 14 of 15 (93.33%) changed or added relevant lines in 1 file are covered.
• 29 unchanged lines in 9 files lost coverage.
• Overall coverage increased (+0.02%) to 80.729%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
apps/emqx_connector/src/mqtt/emqx_connector_mqtt_worker.erl	14	15	93.33%

Files with Coverage Reduction	New Missed Lines	%
apps/emqx_gateway/src/mqttsn/emqx_sn_channel.erl	1	73.04%
apps/emqx/src/emqx_broker.erl	1	84.83%
apps/emqx/src/emqx_cm.erl	1	89.91%
apps/emqx/src/emqx_config.erl	1	86.51%
apps/emqx/src/emqx_message.erl	1	94.83%
apps/emqx_resource/src/emqx_resource_buffer_worker.erl	3	93.04%
apps/emqx_resource/src/emqx_resource_metrics.erl	5	74.07%
apps/emqx/src/emqx_sys_mon.erl	5	86.46%
apps/emqx/src/emqx_reason_codes.erl	11	89.71%

Totals
Change from base Build 4145286896:	0.02%
Covered Lines:	23694
Relevant Lines:	29350

---

💛 - Coveralls