[Config] Document 'compat' configuration settings

[andreyaksenov]

Product: Tarantool
Since: 3.0
Root document:

• A new compat section in the Configuration reference.
• https://www.tarantool.io/en/doc/latest/reference/reference_lua/compat/

SME: @ Totktonada

Details

Options:

• https://github.com/tarantool/tarantool/blob/f58bfc97c627f1838696697339fb3e443c05767a/src/box/lua/config/instance_config.lua#L2227

[andreyaksenov]

Duplicates #3937