Add DTLS support to socket echo_client and echo_server samples.
Additionally, move TLS-related configs to overlay-tls.conf config file,
to align with other examples.
Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>
This commit adds TLS support to socket echo_client/echo_server samples.
Credentials used are the same as in the non-socket versions of these
samples, therefore they can be easily tested with net-tools utils.
Maximum payload size for the client was sligtly reduced to fit the
encrypted data within 1280 bytes.
Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>