[docs] add Doxygen group for new TCP Abstractions API (#7647)
[docs] add Doxygen group for new TCP Abstractions API (#7647)


abtink/openthread,openthread/openthread,abtink/openthread,jwhui/openthread,srickardti/openthread,jwhui/openthread,jwhui/openthread,srickardti/openthread,jwhui/openthread,srickardti/openthread,srickardti/openthread,abtink/openthread,abtink/openthread,openthread/openthread,openthread/openthread,openthread/openthread