Introduces the 'io.openems.edge.bridge.mqtt' module, providing MQTT communication support for OpenEMS Edge with MQTT 3.1, 3.1.1, and 5.0 via HiveMQ client. Adds configuration, connection handlers, API interfaces, and subscription management. Updates build and application files to include the new bridge and its dependencies.

This commit replaces the HiveMQ client with the Eclipse Paho client for both MQTT 3.x and MQTT 5.0 connection handlers in the MQTT bridge component. The change includes adapting the connection, publishing, subscription, and disconnection logic to utilize the Eclipse Paho API. This upgrade addresses compatibility issues with the previous client and improves the stability and flexibility of MQTT communications. The implementation now supports detailed configuration options provided by Eclipse Paho, such as automatic reconnection handling, advanced authentication mechanisms, and Last Will and Testament (LWT) features. Additionally, the commit introduces a custom reconnection strategy and enhances the handling of MQTT message subscriptions and deliveries, ensuring more robust and reliable MQTT service integration.

This commit introduces a dummy implementation of the MQTT bridge (`DummyBridgeMqtt.java`) and its corresponding unit tests (`BridgeMqttImplTest.java`). Additionally, it includes package information (`package-info.java`) for proper OSGi bundle export. The dummy implementation is designed for use in unit testing by providing a mock MQTT bridge environment. This allows for testing of MQTT-related functionalities without the need for an actual MQTT broker connection. The removal of the Checkstyle build command and nature from the `.project` file suggests a simplification of the build process, possibly to streamline development or due to the Checkstyle configuration being managed differently.

This commit removes the HiveMQ MQTT client shaded dependency from the cnf/pom.xml file. As it is not needed!

Co-authored-by: Felix S <[email protected]>