Refactored the handling of observer-related settings by moving them from
NodePrefs to a new MQTTPrefs structure. This change centralizes MQTT,
WiFi, timezone, SNMP, and alert configurations, improving code organization
and maintainability. The new structure allows for better separation of
concerns and prepares the codebase for future enhancements.
Refactored the CommonCLI class to separate observer-related command
handling into CommonCLI_Observer.cpp. This change improves code
organization and maintainability by isolating MQTT, WiFi, and other
observer-specific commands from the main CLI logic.