analyze_object's tuple observations are not registered in final processed results file

[JorgeGtz]

Describe the bug The two observations of type tuple in the function analyze_object (center_of_mass and ellipse_center) don't get registered in the file resulting from process_results.

The intermediary .json file does contain the observations.

@HaleySchuhl points out that in save_results lines 158-166 of classes.py tuple values are not being unpacked.

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

1. Run analyze_object
2. Run outputs.save_results
3. Run parallel.process_results on the results folder
4. Run plantcv-utils.py json2csv to obtain the csv files where the observations are missing

Expected behavior The observations should be registered in either the single-value-traits or the multi-value-traits files.

Local environment (please complete the following information):

• OS: Linux
• Environment conda
• PlantCV Version 3.12.0

Additional context