OPENTHREAD_CONFIG_SRP_SERVER_DEFAULT_ADDRESS_MODE macro

@def OPENTHREAD_CONFIG_SRP_SERVER_DEFAULT_ADDRESS_MODE Specifies the default address mode used by the SRP server. The address mode specifies how address and port number are determined by the SRP server and how this info is published in the Thread Network Data. The value of this configuration should be from `otSrpServerAddressMode` enumeration.