[clang] [analyzer] Reject non-symbolic iterator offsets (PR #232622)

[via cfe-commits]

relaxcn wrote:

> Looks good to me, not crashing is better than crashing.
> 
> Let's wait a few days in case somebody wants to add something (unless merging this is urgent for you); then I'm happy to help you with the merging (when you say that it's ready).

Thank you. This is not urgent. We could wait for other comments.

https://github.com/llvm/llvm-project/pull/232622