Add new stats Storage Usage

[haison8x]

Is your feature request related to a problem? Please describe

My docker container generates several files a minute, after a while, the portainer stats shows that my container used more than 2GB RAM. If the generated files are deleted, the memory usages decrease to 100Mb

I think the memory usages showed on portainer included the storage usages.

Describe the solution you'd like

The portainer stats should have the storage usages

Describe alternatives you've considered

NA

Additional context

NA