CAMEL-23160: camel-core - Add type converter for camel-util-json

[davsclaus]

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[github-actions]

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[gnodet]

Minor observations:

1. convertToJson() casting — The JsonObject converter casts exchange.getIn().getBody() directly. If the body is a primitive JSON value (string, number), this would throw ClassCastException. However, this is consistent with how other converters in the codebase work (Camel's type converter framework handles the routing).
2. Shorthand aliases — The PR adds aliases like JsonObject, JsonArray, and Json (for Jsonable) in resolveClass(), but only for the single-arg overload. The ClassLoader-specific overloads don't get the aliases. This is fine for typical usage (convertBodyTo("JsonObject")).
3. Missing test coverage — There's no test for the Json → Jsonable alias specifically, though the converter tests cover the underlying conversion.