[Debug Info] add a template class DITypedArray.

[Debug Info] add a template class DITypedArray.

Typedef DIArray to DITypedArray<DIDescriptor>. Also typedef DITypeArray as
DITypedArray<DITypeRef>.

This is the third of a series of patches to handle type uniqueing of the
type array for a subroutine type.

This commit should have no functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214115 91177308-0d34-0410-b5e6-96231b3b80d8