Connected new callback functions at nfapi_pnf for phy_stub mode + Intorducing new functions initializing UE variables and threads specific to phy_stub mode, instead of extending the existing ones + Direct connection of the timer_thread with UE_phy_stub_thread_rxn_txnp4.

Introduce nfapi_mode variable to differentiate functionality between phy_stub_ue mode (nfapi_mode=3) and normal full stack mode (nfapi_mode!=3).

Added functions copying nfapi requests to UE_mac_inst + Substituted calls to phy_procedures_ue rx/tx with phy_stub functions triggering MAC layer Tx/Rx procedures at UE MAC. Changes within UE_thread_rxn_txnp4

update SidelinkUEInformation (UE's side), RRCConnectionReconfiguration (eNB's side), add rrc_ue_process_radioResourceConfig to process RPs and configure MAC/PHY

Added handling of HI_DCI0_config requests at UE MAC. Eliminated calls to PHY functions from utilized UE MAC functions (e.g., ue_send_sdu) to support phy_stub operation mode.

Updated handling of DL_config and Tx_req pdus in phy_stub_UE to be compliant with nfapi callback functions

Added MAC level state variable for the UE and control mechanisms to ensure the correct operation of the UE MAC state machine.

uplink data from ue received, corrected scheduling of DCI0/UPLINK_CFG.  Fails to correctly form (SFNSF) for PHICH ACK

Added remaining fill_harq indication functions + the functionality to handle ul_config request pdus arriving from nfapi-vnf: trigger the appropriate UE_MAC and fill_indication functions to prepare the UL_indications which will be put into the socket for transfer back to vnf. Main changes within phy_stub_UE().

Change +4 for tx to a variable and get it to run at +2, this alllows nFAPI to get the reply back for HI_DCI0 to generate the PHICH in time

Crashes around msg4 time, but understand that need to get the ACK for the UE UL of msg3 back to UE within 4ms

- remove global variables in the function lte_est_timing_advance_pusch
- do the smoothing logic that was in lte_est_timing_advance_pusch
  in rx_sdu (is it necessary? is it correct?)
- put back the value 100 in prach_procedures for the test on prach energy
- change the value of timing_advance_update

  it was:

     timing_advance_update                  = sync_pos - eNB->frame_parms.nb_prefix_samples/4; //to check

  it is now:

     timing_advance_update                  = sync_pos; // - eNB->frame_parms.nb_prefix_samples/4; //to check

  this should be checked somehow. The computation looked suspicious. Maybe
  the new one is wrong.

- compile with warning enabled (changes in CMakeLists.txt)
- remove warnings that were present

- allocate memory, memory on stack does not survive the function
- avoid uint32_t, use a char buffer, for endianness neutrality