Count dominating child field values

Context

uniqueBlock(root) which was introduced in SOLR-8998 allows to count child field facet grouping hits by parents, ie hitting every parent only once.

Problem

How to count only dominating child field value. ie if a product has 5 Red skus and 2 Blue, it contributes Red(1), Blue(0)

Suggestion

Introduce dominatingBlock(root) which aggregate hits per parent, chooses the dominating one and incs only it.

Further Work

Judge dominating value not by number of child hits, but by the given function value. Like pick the most popular, best selling, random child field value as dominating.