Prevent illegal `max_query_terms` values in MLT query

[cbuescher]

The MoreLikeThisQueryBuilder and MoreLikeThisQuery can be created with illegal max_query_terms values (e.g. negativ or 0 values). This can lead to NPEs as demonstrated in #48007. We should check and reject those values in the relevant places (e.g. setters) in the builder and the query.

[elasticmachine]

Pinging @elastic/es-search (:Search/Search)