[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
16 files changed