SWDEV-209060 - Create the Skeleton RDC CLI and daemon

Create the skeleton implementation of rdc_client.so and rdci. Modify current rdcd to
integrate the RDC API service:

rdc.proto is changed to add a new RdcAPI service which defined the interfaces for the RDC API.

RdcStandaloneHandler.cpp is added to send the request using gRPC to the rdcd. It is built into
the rdc_client.so

rdci.cc, RdciDisCoverySubSystem.cc and RdciSubSystem.cc are added to implement skeleton rdci.
Currently, the discovery subsystem is supported.

rdc_api_service.cc is added to the server as a skeleton to implement the RdcAPI service. Currently,
only discovery API is implemented. Note: we disabled the rdc_rsmi_service, which will be removed
in the future. The original rdc_client.so is renamed to rdc_client_smi.so which should also be
removed in the future.

Add the instruction how to run the rdcd and rdci in the build folder in the README.md.

Change-Id: Id232f9f83787e5812d4a295dc8cf0daa7728b06c

rdc_libs/bootstrap/src/RdcBootStrap.cc

@@ -320,6 +320,8 @@ const char* rdc_status_string(rdc_status_t result) {
                 return "The max limit reached";
         case RDC_ST_CONFLICT:
                 return "Conflict with current state";
+        case RDC_ST_CLIENT_ERROR:
+                return "RDC Client error";
         default:
                 return "Unknown";
     }