Replace deprecated thrust::identity type

The `thrust::identity` was deprecated and subsequently removed in CCCL
3.0 which ships with CUDA 13.0. Thus, our use of this type blocks us
from switching to CUDA 13.0. This commit amends this problem by
switching to a custom function object.

Author: stephenswat

device/cuda/src/ambiguity_resolution/greedy_ambiguity_resolution_algorithm.cu

@@ -39,6 +39,13 @@
 #include <thrust/unique.h>
 namespace traccc::cuda {
 
+struct identity_op {
+    template <typename T>
+    TRACCC_HOST_DEVICE T operator()(T i) const {
+        return i;
+    }
+};
+
 // Device operator to calculate relative number of shared measurements
 struct devide_op {
     TRACCC_HOST_DEVICE
@@ -200,7 +207,7 @@ greedy_ambiguity_resolution_algorithm::operator()(
     auto cit_begin = thrust::counting_iterator<int>(0);
     auto cit_end = cit_begin + n_tracks;
     thrust::copy_if(thrust_policy, cit_begin, cit_end, status_buffer.ptr(),
-                    pre_accepted_ids_buffer.ptr(), thrust::identity<int>());
+                    pre_accepted_ids_buffer.ptr(), identity_op{});
 
     // Sort the flat measurement id vector
     thrust::sort(thrust_policy, flat_meas_ids_buffer.ptr(),