A WIP patch makes `DIDescriptor` accessors more strict, which in turn
causes the `DebugInfoFinder` to crash on wrongly typed `!dbg`
attachments. Catch that error up front in
`Verifier::visitInstruction()`.
Also remove a test that we "handle" invalid `!dbg` attachments, added
back in r99938. We don't want to handle those anymore.
Note: I'm *not* recursing and verifying the debug info graph reachable
from this node; that work is already done by `verifyDebugInfo()`.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232834 91177308-0d34-0410-b5e6-96231b3b80d8