[Java] support for Externalizable serialization

[chaokunyang]

Is your feature request related to a problem? Please describe.
Serialization for classes implementing Externalizable should be handled in a new serializer for efficiency. Using JavaSerializer will have jdk serialization cost.

Describe the solution you'd like
Using FuryObjectOutput and FuryObjectInput in #138 as parameters for writeExternal/readExternal invocation.

Additional context
#138