Make all built-in modules visible by default in the interactive console

[Totktonada]

Tarantool version: 2.7.0-74-g71377c28e.

It would be convenient to use, say, fiber.info() without explicit fiber = require('fiber') in the interactive console. The same for all other built-in Lua modules.

I would not place them all into _G: it would direct users to omit explicit require calls in modules and applications that may look confusing for a reader. I guess we can run a code from the interactive console in a specific scope, which contains all those variables.

The idea was issued by @Mons, when we forgot a require call at writting a code snippet in the console.

[kyukhin]

Looks like a feature for the 3 series.