Refresh Information Architecture — Phase 2

This epic is phase two of the information architecture refresh for devex documentation. Phase two includes: migrating information architecture refresh to Server developer docs in release/7.6; combining the Search developer guides with the existing Search reference material.

The long-lived feature branches for phase two are:

• https://github.com/couchbase/docs-server/tree/DOC-11965-ia-refresh-76
• https://github.com/couchbaselabs/docs-devex/tree/DOC-11965-ia-refresh-76

I've carried over some outstanding leftover tickets from phase one to this epic.