[noimplicitcopy] When serializing SIL types, always use getRawASTType() instead of getASTType() to prevent us from looking through no implicit copy types while serializing.

This change makes sense since, in general, when serializing we do not want to
look through no implicit copy types since we are trying to 1-1 preserve the
SIL.

(cherry picked from commit f88fa66)

Author: gottesmm