Update and add new information to 7.6 Eventing documentation (Server)

Copy of Cloud epic https://couchbasecloud.atlassian.net/browse/AV-68986

The Eventing docs have been neglected for some time and need a big overhaul. I’ll add more information here and open doc issues as I explore and define what needs to be done.

PM: Jon Strabala

Existing Eventing docs:

• Server: https://docs.couchbase.com/server/current/eventing/eventing-overview.html

• Capella: https://docs.couchbase.com/cloud/clusters/eventing-service/eventing-service.html

Jon’s slides from 2021: https://docs.google.com/presentation/d/1mH8PczM2aHfU4QHnlroPTVou9Hm9sP4oWYq_rnLI_fU/edit#slide=id.gf7ca5c9025_0_917

7.6 Eventing updates: https://docs.google.com/presentation/d/11FpUOa2iH1yVErPHEbVe2IcU3gs5RTNGqcAP4SrTAUw/edit#slide=id.g11421314f2c_0_0