* Cross language serialization for Java and Python
* Use strict types when Python serializing
* Handle recursive objects in Python; Pin msgpack >= 0.6.0, < 1.0.0
* Disable gc for optimizing msgpack loads
* Fix merge bug
* Java call Python use returnType; Fix ClassLoaderTest
* Fix RayMethodsTest
* Fix checkstyle
* Fix lint
* prepare_args raises exception if try to transfer a non-deserializable object to another language
* Fix CrossLanguageInvocationTest.java, Python msgpack treat float as double
* Minor fixes
* Fix compile error on linux
* Fix lint in java/BUILD.bazel
* Fix test_failure
* Fix lint
* Class<?> to Class<T>; Refine metadata bytes.
* Rename FST to Fst; sort java dependencies
* Change Class<?>[] to Optional<Class<?>>; sort requirements in setup.py
* Improve CrossLanguageInvocationTest
* Refactor MessagePackSerializer.java
* Refactor MessagePackSerializer.java; Refine CrossLanguageInvocationTest.java
* Remove unnecessary dependencies for Java; Add getReturnType() for RayFunction in Java
* Fix bug
* Remove custom cross language type support
* Replace Serializer.Meta with MutableBoolean
* Remove @SuppressWarnings support from checkstyle.xml; Add null test in CrossLanguageInvocationTest.java
* Refine MessagePackSerializer.pack
* Ray.get support RayObject as input
* Improve comments and error info
* Remove classLoader argument from serializer
* Separate msgpack from pickle5 in Python
* Pair<byte[], MutableBoolean> to Pair<byte[], Boolean>
* Remove public static <T> T get(RayObject<T> object), use RayObject.get() instead
* Refine test
* small fixes
Co-authored-by: 刘宝 <po.lb@antfin.com>
Co-authored-by: Hao Chen <chenh1024@gmail.com>
