[ADT] Use a C++17 fold expression in hash_combine (NFC)#159901

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

kazutakahirata:cleanup_20250919_10TMP_ADT_hash_combinerkazutakahirata/llvm-project:cleanup_20250919_10TMP_ADT_hash_combinerCopy head branch name to clipboard