[Java] Add StringBuilder/StringBuffer serializer

[chaokunyang]

Is your feature request related to a problem? Please describe.
Add StringBuilder/StringBuffer serializer

Describe the solution you'd like
Convert StringBuilder/StringBuffer to String, then serializing it using StringSerializer.

Describe alternatives you've considered
Convert to/from String may have some cost, bettern solution is tackle inner data structure of StringBuilder/StringBuffer directly.
But StringBuilder/StringBuffer serialization is not common, we can using the conversion first, then optimize later if truely needed.
Additional context
#89