[Epic] Doc restructurization

[veod32]

Possible docs structure: https://docs.google.com/document/d/15n-GlYfuKBqak_flOrlM-Mrm3nmfSUZ1N2as8XxXsj4/edit?usp=sharing

New structure PoC: #4263.

Here is the list of related issues. We can take some ideas and close them later:

• Sort information about connectors #2667
• Move pages from Reference #3180
• Create the new Developer's guide section #3179
• [Epic] Restructure docs, stage 3 #3175
• [Tech debt] Restructuring Tarantool docs #2051

[andreyaksenov]

Comments from R&D:

• Rename Database & application server to Tarantool platform guide or smth like that.
• Move Transactions right after Defining and manipulating data.
• Move Configuration at the first or second place in the section's hierarchy.
• Remove top-level LuaJIT.
• Move Tooling right after the Platform guide.