unnecessary error msg in reference line provider.

Planning: use two step qp st search process. use smaller acceleration range in the first step, if not possible, extend the acceleration range and search again.

Planning: (1) fixed smooth issue by adjusting parameters. (2) Increased planning robustness with sacrificing the initial continuity of acceleration.
(2) comes from an intrinsic issue when we use spline curves to fit all planning results ---- NOT all cases can be fitted by spline!
We should evaluate the necessity of using splines, especially when the
cost is that planning might fail in some cases. In the future version, we should not focus only
on the smoothness of the curves. Perfect smoothness can only live in an unrealistic imaginary world.
We should also notice that the smoothness of planning results doesn't
exactly correlate to what people feel when sitting on a car.

Planning: changes for follow algorithm. (1) make sure acceleration is < 0 when the adc is between the front car and follow fence; (2) only add follow reference point when the point is behind reference line; (3) added parameter follow_drag_distance to adjust following behavior.

Planning: fixed follow issue in qp_st_graph. The reference line of follow should only be set when time is within the boundary range.

Planning: removed low velocity threshold. Planning will report the idea trajectory and control will set a cut off number in its own algorithm.

Planning: (1) adjust lateral/longitudinal bound in reference_line_smoother to provide near to center reference lines; (2) adjust the speed lower bound from 0.0 to 1e-12 to avoid double precision issue in qp_st_speed_graph.

* Planning: set use_ros_time default conf to false.

* Planning: relaxed the jerk continuity requirement for better robustness.

* Planning: fixed bug when generate init speed profile.

* pnc_map: style changes in pnc_map/path.h/cc

* Planning: Added acceleration constraint in qp_st_spline_speed.

whose max_s or max_t is < 0.

Planning: fixed a bug in getting speed limit. std::lower_bound return iterator to vector end, not the last item.

* prepare to migrate st_boundary to path_obstacle.

Planning: use binary_search to speed up the algorithm to get speed limits in QpSplineStGraph. (#966)

bugfix: fix reference guide line bug
add unit test

Planning: revert changes of speed_limit because t info is needed. fixed some bugs in qp_spline_st_graph.