Add a name to ScriptGroup2.Builder.create method

The name is not used in any meaningful way yet, but would be used
to name the file for generated code for fused kernels in other
coming CLs.

A script group name cannot be null or empty, or longer than 100
characters. It can only contain letters, digits, '-', or '_'.

Change-Id: I95fdbf58e6689da91ca98c2057dfa1a803d3b27b