Improve store get_info with collection data for VersionStore

[dimosped]

We need to improve the available meta-data we keep for the data usage of a given library.

Extend capabilities of get_info with :

• collection size
• size of old versions
• size of orphaned segments
• last access time the collection was accessed
• number (maybe size) of versions accessed each day

The user may create standardized Arctic Prometheus metrics for the above, with option to start prometheus web server ready for scraping.

The goal is to help understanding space usage providing insights for data eligible for deletion.

This could also help with solutions of multi tier storage (e.g. hybrid mongo(where most recently accessed data go) and nfs/s3(slower easier to maintain, slower retrieval))

[dimosped]

Use Prometheus in your Python code:
https://github.com/prometheus/client_python

Spin up your own local Prometheus server:
https://prometheus.io/docs/prometheus/latest/getting_started/