Add delegation/staking statistics: total staked (Nova) [medium]

[begonaalvarezd]

Description

Priority: medium

This is part 1 of 4 statistics we would like to have for delegation/staking statistics. The idea of this feature is to know how much is staked in total in the staking feature of all accounts

The 4 parts are:

1. total staked
2. total staked in committee
3. total delegated
4. total delegated in committee

Motivation

Improve statistics to accomodate to new IOTA 2.0 features, like delegation/staking statistics

Requirements

Open questions (optional)

Are you planning to do it yourself in a pull request?

No.

[DaughterOfMars]

This is implemented in the features measurement