Add new performance metrics

[oxarbitrage]

We want to have more data to feed our dashboard, for example we want to have cumulative transactions, shielded inputs, outputs, etc.

This discussion is to figure out what exactly we will want to see so we can open tickets for implementing.

[oxarbitrage]

Let's just discuss specifics when required or requested, a generic plan for performance metrics is not something we will want to do now.