samples: echo_client: Add overlays for debugging

Add overlays that might be useful for debugging:

- overlay-log.conf
   Enable debug log for socket, context, connection, TCP/TCP2.
- overlay-debug.conf
   Disable optimization and compile with debug information.
- overlay-max-stacks.conf
   Overlay to quickly sort out insufficient stack problems.
- overlay-e1000.conf

Signed-off-by: Oleg Zhurakivskyy <oleg.zhurakivskyy@intel.com>