* add backend_ipc.{cpp & hpp}
* rename context_ipc.{cpp & hpp} to context_ipc_device.{cpp & hpp}
* add host interface to IPC backend
* add context_ipc_host.{cpp & hpp} to support host interface
* add USE_RO compile flag to enable support for single backend interface at a time
* add ipc_single script to build rocSHMEM with IPC backend
[ROCm/rocshmem commit: 49779863c2]
mv ipc_policy.{hpp,cpp} into a separate folder as a start for the
standalone IPC conduit.
Unit tests and functional tests pass on the developmpent system.
[ROCm/rocshmem commit: 1183006e20]
avinashkethineedi
Brandon Potter
Edgar Gabriel