The order of disjuncts in DisjunctionMaxQuery affects equals()

See [Lucene-9940](https://issues.apache.org/jira/browse/LUCENE-9940). I find it valid for current Lucene.Net.

DisjunctionMaxQuery stores its disjuncts in a java array, and its equals() implementation uses Arrays.equal() when checking equality. This means that two queries with the same disjuncts but added in a different order will compare as different, even though their results will be identical. We should replace the array with a Set.

Fix it may break current behavior, but in case someone need it, I will create a PR.

Start with DisjunctionMaxQuery.equals() and the representation of its disjuncts. Verify how equality currently treats insertion order, then check related query-equality coverage and compatibility concerns; done means queries containing the same disjuncts compare consistently regardless of insertion order.

Written by the indexing model from the issue text.