[ResponseOps][Terraform] Update Connector resource implementation

[adcoelho]

Summary

Similar to what was done for the Maintenance Window resource, the implementation of the connector resource(elasticstack_kibana_action_connector) in the ElasticStack Terraform provider should be migrated from the sdkv2 to the plugin framework.

Additionally, the client used should be the kibana_oapi generated from the OpenApi specification.

I think this implementation would fixe the following bugs:

• [Bug] Connector Import sets secrets to null for type .webhook #634
• [Bug] connector_id is not used when creating an alerting connector #1088