java: add MQTT auto reconnect to IoT3 Core

[mathieu1fb]

Feature

The IoT3 Core MQTT client now has an automatic reconnection policy: reconnection will automatically be tried 500 ms after a connection loss the retry delay will gradually increase up to every 5 seconds.

The IoT3 Core and Mobility also expose respectively an isMqttConnected() and isConnected() method.

Closes #323

---

How to test

1. Clone the its-client project on your IDE.
2. Ensure that you have Gradle to be able to build the java/iot3 modules (core, mobility and examples).
3. Find the Iot3MobilityBootstrapExample class in the examples module, and set appropriate values for the following fields:

private static final String EXAMPLE_UUID = "uuid";
private static final String EXAMPLE_CONTEXT = "context";
// Bootstrap parameters
private static final String BOOTSTRAP_ID = "bootstrap_id";
private static final String BOOTSTRAP_LOGIN = "boostrap_login";
private static final String BOOTSTRAP_PASSWORD = "bootstrap_password";
private static final BootstrapHelper.Role BOOTSTRAP_ROLE = BootstrapHelper.Role.EXTERNAL_APP;
private static final String BOOTSTRAP_URI = "bootstrap.uri.com";
private static final boolean ENABLE_TELEMETRY = false;

4. Run Iot3MobilityBootstrapExample.
5. After a few seconds, disconnect your computer from the Internet (turn WiFi off or disconnect your Ethernet cable).
6. After another few seconds, reconnect your computer to the Internet.

---

Expected results:

1. On the console, you should see the following:

Bootstrap success
IoT3 ID: <id>
LOGIN: <login>
PASSWORD: <password>
MQTT URI: <mqtt_uri>
TELEMETRY URI: <open_telemetry_uri>

2. On the console, you should then see that the MQTT connection has been established successfully and that mobility messages are being published and received periodically (CAM, CPM and DENM).
3. After disconnection, you should not receive the messages anymore.
4. After reconnection, you should start receiving messages again.

[fredOG-2A1]

I confirmed that reconnection ik OK:
Bootstrap success
IoT3 ID: o...t
LOGIN: e...p
PASSWORD: ...
MQTT URI: mqtts://d...5
TELEMETRY URI: https://m...t/
...

`Bootstrap success
IoT3 ID: o...t
LOGIN: e...p
PASSWORD: ...
MQTT URI: mqtts://d...5
TELEMETRY URI: https://m...t/
...

mars 17, 2025 9:26:59 AM com.orange.iot3core.clients.MqttClient publishMessage
INFOS: Sending message: default/inQueue/v2x/cam/...,"timestamp":1742200016921}
CAM received: {"origin":"self","source_uuid":"ora_iot3mobility_test","type":"cam"...,"timestamp":1742200016921}

//First message with no corresponding reception.
mars 17, 2025 9:27:10 AM com.orange.iot3core.clients.MqttClient publishMessage
INFOS: Sending message: default/inQueue/v2x/cam/...,"timestamp":1742200028015}
mars 17, 2025 9:27:10 AM com.orange.iot3core.clients.MqttClient onPublishComplete

//Mqtt related infos.
mars 17, 2025 9:27:29 AM com.orange.iot3core.clients.MqttClient lambda$new$0
MQTT Connection lost...
INFOS: Disconnected from MQTT broker default.mobility-integration.ocb.itsplatform.eu

//Mqtt reconnection
mars 17, 2025 9:27:30 AM com.orange.iot3core.clients.MqttClient lambda$new$1
INFOS: Connected to MQTT broker default.mobility-integration.ocb.itsplatform.eu
MQTT connection complete: default.mobility-integration.ocb.itsplatform.eu

//Messages are received.
mars 17, 2025 9:27:31 AM com.orange.iot3core.clients.MqttClient publishMessage
INFOS: Sending message: default/inQueue/v2x/cam/...,"timestamp":1742200048153}
CAM received: {"origin":"self","source_uuid":"ora_iot3mobility_test","type":"cam",...,"timestamp":1742200048153}
`