A follow-up commit refactors the filling of information of DRBs to set
up in a separate function (to be reused for handover later). Hence, we
cannot store the DRB TEID/address in the same information, because it is
a logically separate step, and might not be available/updated.

In e1_send_bearer_updates(), we send the DL (DU) TEID and address to the
CU-UP. Therefore, correct the variable names to reflect that the F1-U
information pertains to the DU.

Also, move the tunnel info update function f1u_dl_gtp_update() to a more
prominent place, and take the pointer to the struct containing the
"interesting" information.

Currently, we are still limited to one Cell by DU, hence looking up a
cell comes down to looking up a DU.

The next commit will modify the UE context setup request procedure to
(possibly) receive UE capabilities through Handover Preparation
Information, which extracts the UE capabilities for the UE to be setup.
To avoid code duplication, extract the code that will be needed in UE
capability extraction from Handover Preparation Information.

Will be reused later for handover.
Co-authored-by: batuhanduyuler <batuhan.duyuler@firecell.io>

Co-authored-by: batuhanduyuler <batuhan.duyuler@firecell.io>

Implement the Transmission Action Indicator F1AP forwarding logic, and
add it to the F1 internal representation structure.

No logic is implemented in this commit.
Co-authored-by: batuhanduyuler <batuhan.duyuler@firecell.io>

Implement the HandoverPreparationInformation F1AP forwarding logic, and
add it to the F1 internal representation structure.

No logic is implemented in this commit.

Refactor the RRC processing timer to be a generic "transmission stop"
timer, and use NR_timer_t for it.

The gNB MAC might need to stop transmission either for some time (RRC
processing), or continuously (transmission stop requested by CU). Those
can be handled in one common timer implementation. The continuous case
will be used in a follow-up commit.

Pass consistently the NR_timer_t object through a pointer. Since we have
to modify all occurrences of is_nr_timer_active(), we use that occasion
and rename that function to nr_timer_is_active() to make it consistent
with all other functions, starting with nr_timer.

Integration: `2024.w23`

See merge request oai/openairinterface5g!2788

* !2510 NR UE MAC UCI on PUSCH and aperiodic CSI reporting
* !2597 LTTng logger (CTF)
* !2751 synch the USRP time accross devices using the host clock
* !2775 Remove some global variables
* !2779 remove rb_mask_ul from permanent storage for stack local usage
* !2782 USRP: add a T trace to record the RX IQ data on antenna 0
* !2783 build_oai: fix bad options' names
* !2753 Pucch power control

This commit introduces LTTng logging mechanism which is an open source
tracing tool.

URL: https://lttng.org/