[Performance] Remove unnecessary synchronization using thrust::cuda::par_nosync policy

[chang-l]

We are always using asynchronous thrust launch on a cuda stream, which involves extra cudaStreamSync within thrust calls, e.g.,

wholegraph/cpp/src/wholememory_ops/functions/exchange_ids_nccl_func.cu

Line 63 in 9f290c4

thrust::cuda::par(allocator).on(stream), seq_indices, seq_indices + indices_desc.size, 0);

wholegraph/cpp/src/wholegraph_ops/unweighted_sample_without_replacement_func.cuh

Line 340 in 9f290c4

thrust::exclusive_scan(thrust::cuda::par(thrust_allocator).on(stream),

It would be better to change to thrust::cuda::par_nosync, to make it easier to overlap with other operations.

[linhu-nv]

Sorry for the late reply. wg 24.04 is closing, is it ok if we fix this in 24.06?