Route IPv6 writes in `switch_stun_packet_attribute_add_binded_address`
and `switch_stun_packet_attribute_add_xor_binded_address` through
`switch_stun_ipv6_t` (16-byte `address[]`) instead of `switch_stun_ip_t`
(4-byte `uint32_t address`).
Add IPv4/IPv6 unit tests for both encoders.
Co-authored-by: Andrey Volk <andywolk@gmail.com>
Dmitry Verenitsin