Co-authored-by: Vladislav <Shpilevoy&lt;v.shpilevoy@tarantool.org>

Closes #4398

@TarantoolBot document
Title: Error objects encoding in MessagePack

Until now an error sent over IProto, or serialized into
MessagePack was turned into a string consisting of the error
message. As a result, all other error object attributes were lost,
including type of the object. On client side seeing a string it
was not possible to tell whether the string is a real string, or
it is a serialized error.

To deal with that the error objects encoding is reworked from the
scratch. Now, when session setting `error_marshaling_enabled` is
true, all fibers of that session will encode error objects as a
new MP_EXT type - MP_ERROR (0x03).

```
    +--------+----------+========+
    | MP_EXT | MP_ERROR | MP_MAP |
    +--------+----------+========+

    MP_ERROR: <MP_MAP> {
        MP_ERROR_STACK: <MP_ARRAY> [
            <MP_MAP> {
                MP_ERROR_TYPE: <MP_STR>,
                MP_ERROR_FILE: <MP_STR>,
                MP_ERROR_LINE: <MP_UINT>,
                MP_ERROR_MESSAGE: <MP_STR>,
                MP_ERROR_ERRNO: <MP_UINT>,
                MP_ERROR_CODE: <MP_UINT>,
                MP_ERROR_FIELDS: <MP_MAP> {
                    <MP_STR>: ...,
                    <MP_STR>: ...,
                    ...
                },
                ...
            },
            ...
        ]
    }
```

On the top level there is a single key: `MP_ERROR_STACK = 0x00`.
More keys can be added in future, and a client should ignore all
unknown keys to keep compatibility with new versions.

Every error in the stack is a map with the following keys:
* `MP_ERROR_TYPE = 0x00` - error type. This is what is visible in
  `<error_object>.base_type` field;
* `MP_ERROR_FILE = 0x01` - file name from `<error_object>.trace`;
* `MP_ERROR_LINE = 0x02` - line from `<error_object>.trace`;
* `MP_ERROR_MESSAGE = 0x03` - error message from
  `<error_object>.message`;
* `MP_ERROR_ERRNO = 0x04` - errno saved at the moment of the error
  creation. Visible in `<error_object>.errno`;
* `MP_ERROR_CODE = 0x05` - error code. Visible in
  `<error_object>.code` and in C function `box_error_code()`.
* `MP_ERROR_FIELDS = 0x06` - additional fields depending on error
  type. For example, AccessDenied error type stores here fields
  `access_type`, `object_type`, `object_name`. Connector's code
  should ignore unknown keys met here, and be ready, that for some
  existing errors new fields can be added, old can be dropped.