Minor fixes/cleanup in NGAP lib
This MR is about a small NGAP-focused cleanup, mainly to reduce clang
warnings and remove dead code.
- Handle unused input parameters in ngap_gNB.c and ngap_gNB_handlers.c.
- Fix clang warning in common/utils/time_meas.h (extra semicolon).
- Removes unused NGAP trace/overload code and related references
(ngap_gNB_trace, ngap_gNB_overload).