Add IPC backend

* 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]

projects/rocshmem/src/roc_shmem_gpu.cpp

@@ -51,8 +51,10 @@
 
 #ifdef USE_GPU_IB
 #include "gpu_ib/context_ib_tmpl_device.hpp"
-#else
+#elif defined(USE_RO)
 #include "reverse_offload/context_ro_tmpl_device.hpp"
+#else
+#include "ipc/context_ipc_tmpl_device.hpp"
 #endif
 
 /******************************************************************************