[ENG-57] Add longest drawdown to backtest

[WillemGerritzen]

What has been changed?

Adds a new metric to the printouts: Longest drawdown (length, and start and end dates).

Actions to be performed before this can be merged

• [x] PR depends on #527
• [ ] Add correct return type hinting: https://github.com/dema-trading-ai/engine/pull/527#discussion_r811010644

[dpulls[bot]]

:tada: All dependencies have been resolved !

[WillemGerritzen]

Move to #532 due to wrong branch