[clang] [CIR] CountOf VLA with Array element type (PR #169404)

[Andy Kaylor via cfe-commits]

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

This looks fine, except for an issue with the test case. The implementation for `evaluateExtent` looks small. Why not include that in this same PR?

https://github.com/llvm/llvm-project/pull/169404