snyk: add latest transform to issues data stream

[efd6]

The new issues data stream has semantics that are similar so threat intel data streams; individual issues may have updates to the backing CVEs that change the meaning/significance of documents to the user. The initial implementation does not update documents after the first retrieval. Document updating via a latest transform should be added.

Ref: https://github.com/elastic/integrations/pull/9924#issuecomment-2126919813

[elasticmachine]

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