Add FluentQuery support to `QuerydslPredicateExecutor` and `QueryByExampleExecutor`

[mp911de]

Based on spring-projects/spring-data-commons#2421, it would make sense to add an implementation for the Fluent Query API through QuerydslPredicateExecutor and QueryByExampleExecutor and their reactive variants. See also spring-projects/spring-data-commons#2228.

[michael-simons]

I cannot make sense of the links you provided. The interfaces mentioned don't have any new default methods in the current 2.6.0 commons snapshot.