[clang][dataflow] Add analysis that detects unsafe accesses to optionals Adds a dataflow analysis that detects unsafe accesses to values of type `std::optional`, `absl::optional`, or `base::Optional`. Reviewed-by: ymandel, xazax.hun Differential Revision: https://reviews.llvm.org/D121197 GitOrigin-RevId: ce205cffdfa0f16ce9441ba46fa43e23cecf8be7