* Make most functional interfaces as `@FunctionalInterface`
* Convert some abstract classes to `@FunctionalInterface` with `default` methods
* Apply Lambda style implementation in some places
* Remove `Function` in favor of similar in Java 8
* Remove redundant code from `DefaultAmqpHeaderMapper` since we are already on Spring AMQP-2.0
* Add several ctors to the `ExpressionEvaluatingMessageListProcessor`
* Populate explicit `Boolean.class` `expectedType` from the `ExpressionEvaluatingReleaseStrategy`
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