Document "Integration of Eventing with SQL++ Analytics" for 7.6

PR: https://github.com/couchbaselabs/docs-devex/pull/138

Preview page: https://preview.docs-test.couchbase.com/eventinganalytics3/server/current/eventing/eventing-language-constructs.html#analytics_call

Document new content for Eventing for the 7.6 Server release.

Integration of Eventing with SQL++ Analytics:

• A new built-in function ANALYTICS() provides integration with SQL++ Analytics directly from Eventing
• Simplifies Eventing code and improves readability
• Eliminates security issues with CURL() from server

Slides: 

• https://docs.google.com/presentation/d/11FpUOa2iH1yVErPHEbVe2IcU3gs5RTNGqcAP4SrTAUw/edit#slide=id.g292548574fe_1_14
• https://docs.google.com/presentation/d/11FpUOa2iH1yVErPHEbVe2IcU3gs5RTNGqcAP4SrTAUw/edit#slide=id.g27bee2a48f9_0_38

Page affected: Eventing Language Constructs