Removed unneeded includes from traits.hpp (rapidsai#7509)

The `cpp/include/cudf/utilities/traits.hpp` file is parsed when building most libcudf source files (~200). This PR removes a couple unneeded header includes to help reduce the compile dependency. Only a couple files needed to be updated that relied on `traits.hpp` including these for them.

Authors:
  - David (@davidwendt)

Approvers:
  - Paul Taylor (@trxcllnt)
  - Jake Hemstad (@jrhemstad)

URL: rapidsai#7509

cpp/include/cudf/utilities/traits.hpp

@@ -16,8 +16,6 @@
 
 #pragma once
 
-#include <cudf/lists/list_view.cuh>
-#include <cudf/structs/struct_view.hpp>
 #include <cudf/types.hpp>
 #include <cudf/utilities/type_dispatcher.hpp>
 #include <cudf/wrappers/durations.hpp>

cpp/src/interop/dlpack.cpp

@@ -15,6 +15,8 @@
  */
 #include <cudf/column/column_factories.hpp>
 #include <cudf/detail/interop.hpp>
+#include <cudf/lists/list_view.cuh>
+#include <cudf/structs/struct_view.hpp>
 #include <cudf/utilities/error.hpp>
 #include <cudf/utilities/type_dispatcher.hpp>
 

cpp/src/io/csv/csv_gpu.cu

@@ -26,6 +26,7 @@
 #include <cudf/lists/list_view.cuh>
 #include <cudf/null_mask.hpp>
 #include <cudf/strings/string_view.cuh>
+#include <cudf/structs/struct_view.hpp>
 #include <cudf/utilities/bit.hpp>
 #include <cudf/utilities/error.hpp>
 #include <cudf/utilities/span.hpp>