Develop extract for time series OVN-K metrics and upload to prometheus

Develop an extract for useful ovn-k metrics, convert them to openmetrics format for upload to a private prometheus instance.  The goal is to first make this available in https://github.com/openshift/network-tools.  Then when high-value metrics are identified build the extract as an option for must-gather.  

See the work in progress here: https://gitlab.cee.redhat.com/cfields/my-network-tools

For reference: OCP Metrics Capture & Visualization

Steps:
Run the script:
./network-tools prometheus-metrics-dump -i=./prometheus-metrics -c
Import the data into a local prometheus instance
./promtool tsdb create-blocks-from openmetrics /tmp/prometheus-metrics-dump.out.openmetrics
Restart the prometheus instance (don't know why this is necessary but new data won't show up until it is restarted
Query the data with appropriate time parameter to look backwards in time:'
./promtool query instant http://localhost:9090 '{_name_=~"ovnkube.*"}[48h]'