[clang] [llvm] [ARM] Add support for Windows SEH (PR #184953)

[Trung Nguyen via cfe-commits]

trungnt2910 wrote:

> I'd like to see IR tests for the backend, along the lines of llvm/test/CodeGen/AArch64/wineh-try-catch*

I added both C tests and IR tests in the latest push. `wineh-try-catch*` don't seem to be applicable since this PR does not guarantee C++ `try`/`catch` support.

I chose `seh-finally.ll` because it was fairly standard across all architectures, and it also helped me catch some bugs in the code.

This code currently passes all the manual tests that I can throw it with. It is failing quite badly on [Microsoft's Windows SEH tests](https://github.com/microsoft/windows_seh_tests), but when I checked ARM64 `clang`, it also failed with the exact same behavior.

https://github.com/llvm/llvm-project/pull/184953