The goals of this task are to:

1. Improve the SBE stage builder so that, for each QSN node type, there is a mechanism for optionally providing a "buildBlockXXX()" method that would act like a "block-based" version of the corresponding buildXXX() method, and add a single "buildBlock()" method that handles dispatching to the appropriate buildBlockXXX() or buildXXX() method.
2. Split buildUnpackTsBucket() into 2 methods: the "block-based" version named 
   "buildBlockUnpackTsBucket()" and the standard version named "buildUnpackTsBucket()".
3. Update buildGroup() to call buildBlock().