Use is_complex_v instead of is_complex<...>::value

Also make Caster object static constexpr in generic copy kernel as it is done in contig kernel.

Author: sycloid

dpctl/tensor/libtensor/include/kernels/copy_and_cast.hpp

@@ -101,7 +101,7 @@ class GenericCopyFunctor
  const ssize_t &src_offset = offsets.get_first_offset();
  const ssize_t &dst_offset = offsets.get_second_offset();
 
- CastFnT fn{};
+ static constexpr CastFnT fn{};
  dst_[dst_offset] = fn(src_[src_offset]);
  }
 };
@@ -237,9 +237,9 @@ class ContigCopyFunctor
 
  static constexpr std::uint8_t elems_per_wi = n_vecs * vec_sz;
 
- using dpctl::tensor::type_utils::is_complex;
- if constexpr (!enable_sg_loadstore || is_complex<srcT>::value ||
- is_complex<dstT>::value)
+ using dpctl::tensor::type_utils::is_complex_v;
+ if constexpr (!enable_sg_loadstore || is_complex_v<srcT> ||
+ is_complex_v<dstT>)
  {
  std::uint16_t sgSize = ndit.get_sub_group().get_local_range()[0];
  const std::size_t gid = ndit.get_global_linear_id();