[clang] [Sema] Fix assertion crash on section conflict with a non-identifier decl (PR #200873)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> The original crash reporter was invalid code, we should be testing the original reproducer case as well as a regression to make sure we are not missing some edge cases.

Good point; @lijinpei-amd can you do that in a follow-up?

https://github.com/llvm/llvm-project/pull/200873