Replace left hand nav with tree view component

[GCHQ-Developer-530]

Summary

Currently, we have a custom component on the guidance site for the left hand nav. Tree view has now been developed so we can replace it with that.

💬 Description

Work should include replacing the left hand nav and all of the nested functionality with tree view.

💰 Use value

Shows a use case of our components.

[gd2910]

This ticket is to move over to tree view, not to change or modify content