[clang] [clang-tools-extra] [clang] NFC: change more places to use Type::getAsTagDecl and friends (PR #155313)

[Matheus Izvekov via cfe-commits]

mizvekov wrote:

> Could this information help you pin-point the issue, or a reproducer is necessary?

@bgra8  Thanks for the heads-up, a reproducer is always helpful, as we can include it in the test suite and make sure it never happens again. Since this involves modules, it probably wouldn't be simple to create a reproducer based on just those hints.

https://github.com/llvm/llvm-project/pull/155313