This is a follow up pull request to #3327 that handles the new JSON API for Spring Data Redis.
It builds upon the command layer from the referenced PR and adds API for the template layer.

Notes:

• BoundJsonOperations is not included yet. Once a version of JsonOperations is approved, the bound operations can be included in this branch.
• RedisJsonTemplate initially felt like a good idea. It creates a separation of concerns, which is nice because the new JSON API does not pair well with a specific V type unlike the other data types in RedisTemplate. However, RedisJsonTemplate feels a little off and maybe a more elegant solution could be derived. It feels more like a configuration class. Maybe we could rename it to RedisJsonConfig. This would also promote developers to inject JsonOperations directly.
• RedisJsonSerializer does not extend RedisSerializer, due to it bringing a lot of functionality that doesn't add any value to the JSON serialization. Furthermore, keeping them separate gives separation of concerns. Also Jedis and Lettuce do not provide byte[] APIs for the JSON commands in Redis, thus making RedisSerializer incompatible.

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