Remove usages of `org.apache.commons.lang3.tuple.Pair` et al

[hatyo]

Part of cutting the dependency on org.apache.commons.lang3 requires finding / implementing alternatives to:

• org.apache.commons.lang3.tuple.Pair.
• org.apache.commons.lang3.tuple.ImmutablePair
• org.apache.commons.lang3.tuple.MutablePair