- configure_fapi_dl_pdu is handling the nfapi_nr_dl_config_request_pdu
 - while configure_fapi_dl_Tx is now handling the nfapi_tx_request_pdu

this was necessary because the computation of the TBS size is needed in the phytest scheduler
before even knowing if there is any data to transmit. The tx_request_pdu must be handled instead
only when there is data to transmit.