[ADT] Reduce code duplication in SmallDenseMap (NFC)#160813

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

kazutakahirata:cleanup_20250925_ADT_SmallDenseMap_allocateBucketskazutakahirata/llvm-project:cleanup_20250925_ADT_SmallDenseMap_allocateBucketsCopy head branch name to clipboard