DebugInfo: Delete DIDescriptor (but not its subclasses)

Delete `DIDescriptor` and update the remaining users.  I'll follow-up by
deleting subclasses in manageable groups (top-down).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235248 91177308-0d34-0410-b5e6-96231b3b80d8
5 files changed