Export total unbound memory usage

[jsha]

Unbound has stats for memory usage by the various caches, and by the various modules. But these don't add up to the total memory usage. For instance message buffers can take up a lot of memory depending on configuration.

It would be great if unbound_exporter could get the current total memory used by unbound (via ps perhaps? Or /proc/) and export that as a metric.

[jpds]

This can be acquired from https://github.com/prometheus-community/systemd_exporter