Create the new Developer's guide section

[patiencedaur]

Epic: Restructure Tarantool docs, stage 3

Related issue: #3180. Do them in a single PR.

Details

• Choose a name: "Developer's guide", "Developer guide", "Development" (compare to "Administration")...

Create a top-level menu item with the corresponding title, next to "Concepts" and "How-to guides".
This is the first part of the task where we take top-level sections and put them under the Dev guide umbrella.

• Move "CRUD operations" to Dev guide. Cross-link from relevant Concepts pages
• Move "Triggers" to Dev guide (from Concepts). Cross-link in relevant places
• Move translations
• Fix links that definitely broke after the changes
• Add redirects after merge (instruction)

Desired structure of the Developer's Guide

Menu item order is TBD.

• Tarantool Lua syntax
• CRUD operations
• Triggers
• Internals (provide external link to tarantool.io/en/dev/core)
• Developing with Cartridge (temporarily link to Cluster on Cartridge)
• Links (one page, below are the contents)
  • Awesome Tarantool
  • Tutorials
  • Best practices
  • Reference

[andreyaksenov]

The Developing applications section is going to be reworked: #3920.
See also: #3817.