[CISA KEV] Modification on connector to use the new pycti connector helper scheduler

[Megafredo]

Proposed changes

• Modification on connector to use the new pycti connector helper scheduler (schedule_iso)
• Catch exception outside running connector process by adding a traceback.print_exc()
• Remove update_existing_data as it is deprecated
• Improve the connector to fill in the "CISA KEV" field (x_opencti_cisa_kev)

Related issues

• Some connectors will pause based on queues threshold opencti#6325
• [CISA KEV] Add scheduler to align with the new way to handle interval (opencti/issue/6325) #2395
• [CISA KEV] Improve connector to populate "CISA Exploited" field #2222

Related PR

• [client] Connector queuing auto backpressure - Scheduler (#6325) client-python#698

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality using different use cases
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

Further comments