JIRA: https://jira.spring.io/browse/INT-3939
Previously `RedisQueueInboundGateway` and `RedisQueueOutboundGateway` used different `RedisSerializer`s
for non-String objects.
* Change the default to the `JdkSerializationRedisSerializer` for the consistency in case of client/server scenarios.
The previous behavior with the `StringRedisSerializer` can be reinstated with `serializer` injection.
Doc Polishing.
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