[MemRef] Migrate away from PointerUnion::{is,get} (NFC)#120202

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

kazutakahirata:cleanup_001_PointerUnion_mlir_Dialect_MemRefkazutakahirata/llvm-project:cleanup_001_PointerUnion_mlir_Dialect_MemRefCopy head branch name to clipboard