preparation for more unit tests

* formalized function names in dp_st_speed graph and cost.

* added num of points in smoother config proto.

After change, the smoother will smooth any given reference line without truncate.
The behavior will be more transparent behavior.

* not a useful base class
* confusing with hdmap path.h

the problem is because LaneWaypoint is not set in hdmap::Path.
fixed the broken unit tests

unify function names