Allow multiple MQTT topics in mqtt-source.json

[shevi-kukis]

Currently, in [mqtt-source.json]
(https://github.com/KamaTechOrg/AgCloud/blob/main/mqtt_and_kafka/connectors/mqtt-source.json#L8)
(https://github.com/KamaTechOrg/AgCloud/blob/main/mqtt_and_kafka/connectors/mqtt-source.json#L12)
,
both mqtt.topics and kafka.topic support only a single topic.

We need to change this so that each team can define its own topic,
by allowing a list of topics in both fields.

Expected:
Each team can add its own topic pair (MQTT + Kafka),
and the connector will handle all of them automatically.