Hardcode (noS1) PDU session ID to 10

Defacto, the PDU session ID for noS1 modes is already hardcoded, as
starting the nr-softmodem with --noS1 --default-pdu-id 1 leads to

    Assertion (entity != ((void *)0)) failed!
    In start_sdap_tun_gnb_first_ue_default_pdu_session() openair2/SDAP/nr_sdap/nr_sdap.c:163

Further, the --default-pdu-id parameter will be deactivated in a later
commit, and we cannot rely on it. Therefore:

- hardcode noS1 PDU ID (also used in --do-ra/--phy-test modes) to 10 and
  use in gNB&UE
- pass the PDU session ID used in SDAP entity initialization down to
  start_sdap_tun_gnb_first_ue_default_pdu_session() to always use the
  correct one

common/platform_constants.h

@@ -100,5 +100,8 @@
 // SDAP
 #define MAX_QOS_FLOWS 64
 
+// SDAP/5G NAS NOS1
+#define DEFAULT_NOS1_PDU_ID 10
+
 #define SPEED_OF_LIGHT 299792458 // in m/s
 #endif /* __PLATFORM_CONSTANTS_H__ */