Deprecate Symantec EDR Cloud integration

[jamiehynds]

We currently have two integrations covering the same Symantec platform, causing user confusion and overlap between two integrations.

Symantec EDR Cloud covers Incidents via Symantec's API. Symantec Endpoint Security covers the same incidents, but also events via object storage.

Rather than maintaining two integrations, can we add a deprecation notice to EDR Cloud and advise customers to move to the SES integration. We can then remove the EDR Cloud integration in 9.0.

[elasticmachine]

Pinging @elastic/security-service-integrations (Team:Security-Service Integrations)