Fix memory alignment issues in hash computation (#338)

When hashing large keys, e.g., strings, we traverse the input key
iteratively in chunks of 4/8 bytes. The current implementation of the
`load_chunk` function falsely assumes that the start of the key is
always aligned to the chunk size, which is not always the case (see
[discussion](rapidsai/cudf#13612 (comment))).

Additionally, this PR fixes some uncaught `[-Wmaybe-uninitialized]`
warnings when compiling the unit tests.

include/cuco/detail/hash_functions/utils.cuh

@@ -21,8 +21,10 @@ namespace cuco::detail {
 template <typename T, typename U, typename Extent>
 constexpr __host__ __device__ T load_chunk(U const* const data, Extent index) noexcept
 {
-  auto const chunks = reinterpret_cast<T const*>(data);
-  return chunks[index];
+  auto const bytes = reinterpret_cast<std::byte const*>(data);
+  T chunk;
+  memcpy(&chunk, bytes + index * sizeof(T), sizeof(T));
+  return chunk;
 }
 
 };  // namespace cuco::detail