Added table and model for instance level destination

...audit_events_instance_external_streaming_destinations.yml

..._audit_events_instance_external_streaming_destinations.rb

db/schema_migrations/20240130162148

db/structure.sql

...s/audit_events/instance/external_streaming_destination.rb

...s/audit_events_instance_external_streaming_destination.rb

...it_events/instance/external_streaming_destination_spec.rb