AI feature usage tracking and GONG_USAGE table updates

The following metrics were added to the GONG_USAGE table:

• ASSISTANT_CHATS: The number of chats started by a user on a specific date
• THEME_SPOTTER_ANALYSIS_GENERATED: The number of AI Theme Spotter analyses generated by a user on a specific date
• THEME_SPOTTER_ANALYSIS_USED: The number of AI Theme Spotter analyses where the user performed an action on a specific date
• MEETING_PREPARATION_USED: Number of meetings for which a user used meeting preparation on a specific date
• PRACTICES_STARTED: Number of AI Trainer practices started by a user on a specific date
• TRAININGS_SUBMITTED: Number of AI Trainer trainings submitted by a user on a specific date
• TRAININGS_STARTED: Number of AI Trainer trainings started by a user on a specific date

The __NEXT fields have been removed from all Gong data cloud tables.