[DataFlow] Migrate away from PointerUnion::{is,get} (NFC)#119950

kazutakahirata merged 2 commits intollvm:mainllvm/llvm-project:mainfrom

kazutakahirata:cleanup_001_PointerUnion_mlir_DataFlowkazutakahirata/llvm-project:cleanup_001_PointerUnion_mlir_DataFlowCopy head branch name to clipboard