[Website]: Document upcoming services/features for Serverless

[lucabelluccini]

Type of issue

None

What documentation page is affected

https://www.elastic.co/docs/deploy-manage/deploy/elastic-cloud/differences-from-other-elasticsearch-offerings

What happened?

Make sure the Serverless Page for O11y gets updated with new intake methods (OTel managed intake service, EDOT cloud forwarder, ...).

Additional info

FYI @chrisdistasio