[clang] [HLSL] Add empty struct test cases to `__builtin_hlsl_is_typed_resource_element_compatible` test file (PR #115045)

[Justin Bogner via cfe-commits]

bogner wrote:

When you change what a PR does, please remember to update the title and description. This went in saying it's about adding some test cases but it actually changes much more than that.

https://github.com/llvm/llvm-project/pull/115045