feat: IPROTO traffic encryption

Add new transport for IPROTO connections: ssl.
SSL transport may be configured with (at client and server side):
- certificate (mandatory at server side)
- private key (mandatory at server side)
- password for PK
- certificate authorities (for peer certificate verification)
- cipher list

SSL transport also can be used in replication and net.box mechanisms.

@TarantoolBot document
Title: add IPROTO traffic encryption.

New ssl transport allows
creating a secure connection between two IPROTO peers.
TLS protocol using and openssl v1.1 or later required.

To configure traffic encryption, you need to set the
special URI parameters for a particular connection.
The parameters can be set for the following box.cfg
options and nex.box method:
- box.cfg.listen – on the server side.
- box.cfg.replication–on the client side.
- net_box_object.connect()–on the client side.