[FEA] cuML and cuGraph sharing of handle and comms

[dantegd]

Is your feature request related to a problem? Please describe.
cuML cuGraph have many needs in common. To be more efficient across projects we should look to share not only algorithmic components but also some infrastructure ones. In particular the cuGraph team wants to adopt the cumlHandle and cumlComms, which definitely can be useful beyond just cuML. This issue is for tracking those efforts.

Describe the solution you'd like
Tasks needed:

• Copy/move handle and required components to raft repository. Rename to raftHandle or rapidsHandle or something.
• Create raft-comms repository: https://github.com/rapidsai/ops/issues/479
• Copy/move cumlcomms to raft-comms repo
• Create binary/conda package of raftComms (or rapidsComms)
• Update cuML to use shared headers/artifact
• Update cuGraph to use shared headers/artifact

Additional context
cuGraph team requires the comms in particular to be moved sooner rather than later, with a target of end of October.

Mirror issue in cuML: rapidsai/cuml#1151

[afender]

This was done as part of the cuGraph OPG and RAFT effort 🎉
#815 to track adoption in existing single GPU features in cuGraph