[clang] [clang] Add test for CWG2149 "Brace elision and array length deduction" (PR #90079)

[via cfe-commits]

https://github.com/cor3ntin approved this pull request.

I'm happy to approve that as is, I expect additional tests to materialize for the rest of the paper.
I'm not concerned about the status page, a new core issue list should materialize any day now

Thanks

https://github.com/llvm/llvm-project/pull/90079