Suggestion replacing Gson with Jackson in default DataConverter implementation

[mr2chethan]

Currently gson is being used in JsonDataConverter https://github.com/cadence-workflow/cadence-java-client/blob/master/src/main/java/com/uber/cadence/converter/JsonDataConverter.java. Gson has many limitations like:

1. Handling LocalDate, LocalDateTime, etc Java 8 date/time types
   ex.

LocalDate date = LocalDate.now();
Gson gson = new Gson();
String json = gson.toJson(date);  // Outputs: "\"2025-04-14\""
LocalDate parsed = gson.fromJson(json, LocalDate.class);  // Exception: can't deserialize

2. Handling polymorphism
   ex.

Animal dog = new Dog();
Gson gson = new Gson();
String json = gson.toJson(dog);  // Loses type info
Animal animal = gson.fromJson(json, Animal.class);  // Deserializes to Animal only, no Dog

3. Performance

Jackson is faster for both serialization & deserialization esp for larger and nested payloads.

I would like to propose replacing Gson with Jackson as the default implementation or providing a first-party JacksonDataConverter alongside the existing Gson one, with an easy way for developers to plug it in.

Happy to contribute a PR if this sounds acceptable.