Skeleton tips easily overwritten within the plantcv.morphology sub-package

[HaleySchuhl]

Describe the bug
Skeleton tips are easily overwritten within the plantcv morphology sub-package since utilizing tips happens in a few other functions as part of the algorithm for sorting or pruning back segments.

To Reproduce
Steps to reproduce the behavior (including sample data and code really help):

1. Starting with image from the morphology tutorial
2. Run function(s) pcv.morphology.find_tips with label=None and then run pcv.morphology.segment_sort or pcv.morphology.prune
3. See error (small green are expected tips, large green are the recorded tip coordinates)
   

Expected behavior
Only save tip coordinates when the function is explicitly ran/

Local environment (please complete the following information):

• PlantCV Version : <= 4.6.0

Additional context
Making a helper function to be able to call within functions and now pcv.morphology.find_tips will be a function that saves to Outputs.observations and is a wrapper of pcv.morphology._find_tips.