[clang] [C23] Fix treating unnamed records nested in different types as compatible. (PR #162933)

[Volodymyr Sapsai via cfe-commits]

vsapsai wrote:

Not sure need to test with `InnerUnnamedStruct_differentNaming`, `InnerUnnamedStruct_differentShape`. I've added those tests because initially - before checking GCC behavior - I've thought we should accept those cases and wanted to get a better coverage in this area.

https://github.com/llvm/llvm-project/pull/162933