Splt BmcInfo into BmcStatus and BmcEndpoint

[ianderson-nvidia]

Separate BmcInfo into BmcStatus and BmcEndpoint and include BmcEndpoint under Machine and BmcStatus under MachineStatus

Look at #2847 (comment) for reference. In Summary

message BmcEndpoint {
  optional string ip = 1;  
  optional string mac = 2;
  optional unit32 port = 3;
  optional common.MachineInterfaceId machine_interface_id = 4;
}

message BmcStatus {
  optional string version = 2;
  optional string firmware_version = 3;
}

message Machine {
...
  BmcEndpoint bmc = 52;
}

message MachineStatus {
...
  optional BmcStatus bmc_status = 25;
}