- included MAC CE sub-PDUs size in the computation of RLC data to transmit
  this fixes the error with residual mac pdu appearing at gNB side when
  transmitting higher amount of data
- got rid of the nr_generate_ulsch_pdu and moved the relevant UL-SCH MAC PDU
  generation procedure within the nr_ue_get_sdu and nr_ue_get_rach
- reduced memcpy calls and unnecessary memory allocations
- fetching RLC data and SDU size from the mac_rlc_data_req, removed the call
  to mac_rlc_get_buffer_occupancy_ind
- introduced a new function to generate the MAC CEs sub-PDUs
- removed unnecessary function input parameters
- minor fixes and cleanup
- enhanced logging