Normalize Activity application architecture

lib/cubit/activity/data_counts_by_day_cubit.dart

lib/cubit/activity/data_counts_by_day_state.dart

lib/cubit/activity/data_counts_by_hour_cubit.dart

lib/cubit/activity/data_counts_by_hour_state.dart

lib/cubit/activity/data_discoveries_cubit.dart

lib/cubit/activity/data_discoveries_state.dart

lib/cubit/activity/data_heatmap_cubit.dart

lib/cubit/activity/data_heatmap_state.dart

lib/cubit/activity/data_new_artists_cubit.dart

lib/cubit/activity/data_new_artists_state.dart

lib/cubit/activity/data_new_tracks_cubit.dart

lib/cubit/activity/data_new_tracks_state.dart

lib/cubit/activity/data_statistics_global_cubit.dart

lib/cubit/activity/data_statistics_global_state.dart

lib/cubit/activity/data_statistics_recent_cubit.dart

lib/cubit/activity/data_statistics_recent_state.dart

lib/cubit/activity/data_timeline_cubit.dart

lib/cubit/activity/data_timeline_state.dart

lib/cubit/activity/data_top_artists_cubit.dart

lib/cubit/activity/data_top_artists_state.dart