DI: Update testcases for LLVM assembly change

Update testcases after LLVM change r243774.

Most of these had no need to check `tag:` field, but did so as a way of
getting to the `name:` field.  In a few cases I've converted the `tag:`
checks to `arg:` or `CHECK-NOT: arg:`.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@243775 91177308-0d34-0410-b5e6-96231b3b80d8