Fix inefficient code related to #1553

[cka-y]

Looking at #1553, there is definitely so inefficient code in there.

For example:

    List<String> uniqueShapeIds =
        shapeTable.getEntities().stream()
            .map(GtfsShape::shapeId)
            .distinct()
            .collect(Collectors.toList());

This is iterating over every line in shapes.txt, when the set of unique shape ids is already available via GtfsShapeTableContainer#byShapeIdMap().

Then, the worst offender:

    uniqueShapeIds.forEach(
        shapeId -> {
          double maxShapeDist =
              shapeTable.getEntities().stream()
                  .filter(s -> s.shapeId().equals(shapeId))
                  .mapToDouble(GtfsShape::shapeDistTraveled)
                  .max()
                  .orElse(Double.NEGATIVE_INFINITY);

For each shape ids, we are again looping over every entry in shapes.txt to find matching shape points. This is where the NxM blow-up and slow-down is likely coming from. Again GtfsShapeTableContainer#byShapeIdMap() already has all the shape points grouped by shape id and should be used directly.

I'd also point out that the shape points and stop points below should both probably be filtered by hasShapeDistTraveled as well.

Originally posted by @bdferris-v2 in #1587 (comment)