Currently configuring embedded_tags for cisco_telemetry_mdt input
requires an unusual mix of - and _, i.e. one needs to specify e.g.
Cisco-IOS-XR-wdsysmon-fd-oper:system-monitoring/cpu-utilization/process_cpu/process-id
for it to work correctly. Additionally, tags created might still contain
dashes against convention.
This fix creates correctly formatted tags with underscores instead of
dashes and unifies the configuration parameter to expect either dashes
or underscores, so old configurations are still valid.
