[TableGen] Migrate away from PointerUnion::{is,get} (NFC)#122569

kazutakahirata merged 1 commit intollvm:mainllvm/llvm-project:mainfrom

kazutakahirata:cleanup_001_PointerUnion_mlir_TableGenkazutakahirata/llvm-project:cleanup_001_PointerUnion_mlir_TableGenCopy head branch name to clipboard