[Conversion] Migrate away from PointerUnion::{is,get} (NFC)#122421

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

kazutakahirata:cleanup_001_PointerUnion_mlir_Conversionkazutakahirata/llvm-project:cleanup_001_PointerUnion_mlir_ConversionCopy head branch name to clipboard