Evaluate VICI as data source

[dennisstritzke]

Currently, the ipsec_exporter uses the output of the ipsec statusall command. This was a quick and easy way to get the exporter working.

As far as I understand the ipsec command uses the VICI protocol to communicate with the daemon. If this is true this could

• make the data collection and general exporter architecture much cleaner, stable and easier to extend
• allow us to run the exporter as an unprivileged user without sudo (making Running ipsec exporter with unprivileged user #27 obsolete by the cleaner data collection approach)
• allow us to run the exporter in a Docker Container (effectively making Add Dockerfile to build an image with our executable #24 possible)
• this might also address issues like support centos based systems #16 & Support libreswan #17
• this might make issues like Feature request: Retrieve metrics for multiple SA's for the same conn #29 & Update exporter to provide count number of connections for each security association #32 much more straight forward to implement (as we would not rely on parsing cmd output anymore)