telemetry: introduce new functionality

telemetry: introduce new functionality

This patch introduces a new telemetry connection socket and handling
functionality. Like the existing telemetry implementation (which is
unaffected by this change) it uses a unix socket, but unlike the
existing one it does not have a fixed list of commands - instead
libraries or applications can register telemetry commands and callbacks
to provide a full-extensible solution for all kinds of telemetry across
DPDK.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Signed-off-by: Ciara Power <ciara.power@intel.com>
Reviewed-by: Keith Wiles <keith.wiles@intel.com>