dgram: add IPv6 scope id suffix to received udp6 dgrams

Add IPv6 link local scope ID suffix to the
rinfo address in those received upd6 datagrams
whose source address is a link local address.

Add a new test case, test-dgram-udp6-link-local-address,
to verify that IPv6 UDP datagrams received from a
link-local source address do contain the scope ID
suffix in the rinfo address field.

When a packet is received from a link-local source
address, if the address does not contain the scope
ID suffix, it is impossible to reply back to the
sender, as the kernel is not able to determine
the right network interface to send the packet
through and returns with an error.

Ref: https://github.com/nodejs/node/issues/1649
PR-URL: https://github.com/nodejs/node/pull/14500

Refs: https://github.com/nodejs/node/issues/1649


Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Stewart X Addison <sxa@uk.ibm.com>