I need to capture the module table inside a module function in a next
commit.

NO_DOC=refactoring, no behavior changes
NO_CHANGELOG=see NO_DOC
NO_TEST=see NO_DOC

Fixes tarantool#9986

@TarantoolBot document
Title: Interactive console now autorequires a couple of built-in modules

There are built-in modules that are frequently used for administration
or debugging purposes. It is convenient to have them accessible in the
interactive console without extra actions.

They're accessible now without a manual `require` call if the
`console_session_scope_vars` compat option is set to `new` (see also
tarantool/doc#4191).

The list of the autorequired modules is below.

* clock
* compat
* config
* datetime
* decimal
* ffi
* fiber
* fio
* fun
* json
* log
* msgpack
* popen
* uuid
* varbinary
* yaml

See tarantool#9986 for motivation behind this feature.

This list forms so called initial environment for an interactive console
session. The default initial environment may be adjusted by an
application, for example, to include application specific administrator
functions.

Two public functions are added for this purpose: `console.initial_env()`
and `console.set_initial_env(env)`.

Example 1 (keep autorequired modules, but add one more variable):

```lua
local console = require('console')

-- Add myapp_info function.
local initial_env = console.initial_env()
initial_env.myapp_info = function()
    <...>
end
```

Example 2 (replace the whole initial environment):

```lua
local console = require('console')

-- Add myapp_info function, discard the autorequired modules.
console.set_initial_env({
    myapp_info = function()
        <...>
    end,
})
```

The `console.set_initial_env()` call without an argument or with a `nil`
argument drops the initial environment to its default.

A modification of the initial environment doesn't affect existing
console sessions. It affects console sessions that are created
after the modification.

Please, adjust the `console_session_scope_vars` compat option
description and extend the built-in `console` module reference with the
new functions.