feat(avoidance): use free steer policy for safety check (autowarefoundation#865)

Signed-off-by: satoshi-ota <satoshi.ota928@gmail.com>

Author: satoshi-ota

autoware_launch/config/planning/scenario_planning/lane_driving/behavior_planning/behavior_path_planner/avoidance/avoidance.param.yaml

@@ -186,6 +186,7 @@
         time_horizon_for_rear_object: 10.0               # [s]
         delay_until_departure: 0.0                       # [s]
         # rss parameters
+        extended_polygon_policy: "along_path"            # [-] select "rectangle" or "along_path"
         expected_front_deceleration: -1.0                # [m/ss]
         expected_rear_deceleration: -1.0                 # [m/ss]
         rear_vehicle_reaction_time: 2.0                  # [s]