COLLECTIONS-867: Switched iterator filters to use java.util.function.Predicate

[Claudenw]

Replaced usage of commons-collections Predicate with java.util.function.Predicate in iterator filtering.

[garydgregory]

Hi @Claudenw

-1: Please see the email thread from way back in July: https://lists.apache.org/thread/44dr03zs4zr92yypgxgsq84273n5g211

Yep, it's a pain, but Collections predates Java 8 and uses custom functional interfaces.

This would be for the next major release so we don't break all existing call sites by breaking binary compatibility.

[Claudenw]

Gary's objection makes sense. Closing this without merging.