neorados: avoid using std::aligned_storage_t

neorados: avoid using std::aligned_storage_t

std::aligned_storage_t was deprecated in C++23, to be prepared for
it, let's use alignas for the same behavior. because we do not always
pass a power-of-2 number to `std::aligned_storage_t`, while `alignas()`
requires an alignment of power of 2. so we use `std::bit_ceil()` to
calculate the minimum alignment greater or equal to the given number.

Signed-off-by: Kefu Chai <tchaikov@gmail.com>