Major Description
Right now [Int/Long/Float/Double]FieldSource can give a ValueSource view of a NumericDocValues field. This Jira is to add MultiValued[Int/Long/Float/Double]FieldSource that given a SortedNumericSelector.Type can give a ValueSource view of a SortedNumericDocValues field
I considered instead of adding new classes an optional selector parameter to the existing [Int/Long/Float/Double]FieldSource, but I think adding different classes makes a cleaner API and it’s clear that for MultiValued* case, the selector is a mandatory parameter.