rrc,ue: for RRC conn release, delay transition to RRC idle by 60ms as per TS 36.331

when receiving RRC connection release all actions shall be delayed by 60ms as
per the standard

lib/include/srsran/test/ue_test_interfaces.h

@@ -29,6 +29,7 @@ public:
   srsran::tti_point get_current_tti() override { return srsran::tti_point{tti % 10240}; }
   void              add_eps_bearer(uint8_t eps_bearer_id, srsran::srsran_rat_t rat, uint32_t lcid) final{};
   void              remove_eps_bearer(uint8_t eps_bearer_id) final{};
+  void              reset_eps_bearers() final{};
 
   // Testing utility functions
   void run_tti()

srsue/src/stack/rrc/rrc.cc

@@ -1098,7 +1098,9 @@ void rrc::rrc_connection_release(const std::string& cause)
 {
   // Save idleModeMobilityControlInfo, etc.
   srsran::console("Received RRC Connection Release (releaseCause: %s)\n", cause.c_str());
-  start_go_idle();
+
+  // delay actions by 60ms as per 5.3.8.3
+  task_sched.defer_callback(60, [this]() { start_go_idle(); });
 }
 
 /// TS 36.331, 5.3.12 - UE actions upon leaving RRC_CONNECTED

srsue/src/stack/rrc/test/ue_rrc_nr_test.cc

@@ -100,9 +100,10 @@ class dummy_sim : public usim_interface_rrc_nr
 
 class dummy_stack : public stack_interface_rrc
 {
-  srsran::tti_point get_current_tti() { return srsran::tti_point(); };
-  void              add_eps_bearer(uint8_t eps_bearer_id, srsran::srsran_rat_t rat, uint32_t lcid){};
-  void              remove_eps_bearer(uint8_t eps_bearer_id){};
+  srsran::tti_point get_current_tti() final { return srsran::tti_point(); };
+  void              add_eps_bearer(uint8_t eps_bearer_id, srsran::srsran_rat_t rat, uint32_t lcid) final{};
+  void              remove_eps_bearer(uint8_t eps_bearer_id) final{};
+  void              reset_eps_bearers() final{};
 };
 
 int rrc_nr_cap_request_test()