UCX synchronize default stream only on CUDA frames (#3638)
UCX synchronize default stream only on CUDA frames (#3638)

* UCX synchronize default stream only on CUDA frames

* Improve check for CUDA frames in UCX comms

* Further improvements to CUDA frame synchronization in UCX

* Fix black formatting
blaze/distributed,dask/distributed,dask/distributed,dask/distributed,dask/distributed,blaze/distributed