[clang] [analyzer][NFC] Add ArrayBoundV2 testcase to document bad cast modeling (PR #108799)

[Donát Nagy via cfe-commits]

NagyDonat wrote:

This PR is primarily a "note to self", but it *is* NFC and ready to be merged if we think that it'd be better to keep this reminder within the repository.

https://github.com/llvm/llvm-project/pull/108799