telemetry: move some functions to metrics library

telemetry: move some functions to metrics library

This commit moves some of the telemetry library code to a new file in
the metrics library. No modifications are made to the moved code,
except what is needed to allow it to compile and run. The additional
code in metrics is built only when the Jansson library is  present.
Telemetry functions as normal, using the functions from the
metrics_telemetry file. This move will enable code be reused by the new
version of telemetry in a later commit, to support backward
compatibility with the existing telemetry usage.

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