Improve Builder.forceName collision errors (#3012)

(cherry picked from commit 0530bdba)

# Conflicts:
#	core/src/main/scala/chisel3/Module.scala
#	core/src/main/scala/chisel3/RawModule.scala
#	core/src/main/scala/chisel3/internal/Builder.scala
#	core/src/main/scala/chisel3/internal/package.scala