std::optional::value() has undesired exception checking semantics and is unavailable in older Xcode (see _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS). The call sites block std::optional migration.
Suggested by @lattner in https://discourse.llvm.org/t/rfc-define-precise-arith-semantics/65507/22. Tested with: `ninja check-mlir check-mlir-integration check-mlir-mlir-spirv-cpu-runner check-mlir-mlir-vulkan-runner check-mlir-examples` and `bazel build --config=generic_clang @llvm-project//mlir:all`. Reviewed By: lattner, Mogball, rriddle, jpienaar, mehdi_amini Differential Revision: https://reviews.llvm.org/D134762
Use a suffix to make clear what the contents inside each file are. Reviewed By: ThomasRaoux Differential Revision: https://reviews.llvm.org/D134202
