Set the list of promotion tiers in a promotion

Set the list of promotion tiers in a promotion.
Promotion tiers are used to define different levels of benefits that customers can receive based on their eligibility.
Each promotion tier has a unique id, a name, and a set of benefits that are applied to customers who meet the conditions of the tier.
Promotion tiers are priority ordered by their index in the array.
Each promotion tier includes a condition tree that defines the conditions under which the tier will be applied.
The condition tree is a hierarchical structure that defines the conditions under which the tier will be applied.
The condition tree is composed of branches, each of which contains a condition that must be met for the tier to be applied.
In order to connect branches into a tree, each branch has a unique id based on its index in the array, and an optional parent field with the index of the parent.
Note that branches may only point to parents in LOWER index than themselves.