documentation

Pull request #1878: feature/ZBX-22307-7.0-D2. New directory structure for database-related files.

Merge in WEB/documentation from feature/ZBX-22307-7.0-D2 to release/7.0

* commit '9009416fb9bf72c8ab563d9b9f656a20be7acb1a':
  [ZBX-22307] added reason for file structure change
  [ZBX-22307] removed mention of "sources" as they've had the new file structure since 6.4
  [ZBX-22307] added missing trends_upgrade.sql files
  [ZBX-22307] clarified `option-patches` directory details
  [ZBX-22307] new directory structure for database-related files