Testing of phy_stub

Necessary modifications to support noS1 with nfapi and eNB side for testing vnf-pnf up to the stage of previous commit

Testing works until the call of callback function pnf_p7_subframe_ind. There, it never satisfies the condition if(tx_subframe_buffer->sfn_sf == sfn_sf_tx) so both sides (vnf and pnf are hanging).

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.

Introduced a new timer_thread within lte-ue. This thread is ticking the subframes and wakes up UE_thread function which is waiting on a condition variable for nfapi_mode=3 (phy_stub)

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().