Moves Statistics class from codjo-sql to codjo-util

## Context
The `Statistics` class wasn't specifically related to SQL but was part of `codjo-sql`.

## Description
- Moves `Statistics` class from `codjo-sql` to `codjo-util`, renames it to `SimpleStatistics` and extracts `Statistics` interface.
- Adds `SegmentedStatistics`, another implementation of `Statistics` that divides time into segments.
- Adds the `TimeUtil` class providing several conversion methods.