[Java] Extensible classloader support

[chaokunyang]

Is your feature request related to a problem? Please describe.
Fury Java JIT will genereate byte codes for generated serializer class, which will be loaded as an class in a new or existed classloader.

Class define and loading should ensure it won't create too much new classloaders, and new classes are eligiable to gc, and doesn't pollute exsting classloaders.

Additional context

#28 #33