Psb 238/remove redundant motion border validation

[mikejhuang]

Changes summary

1. Remove duplicate logic for checking if an roi is in the motion border
2. Renamed is_in_motion_border to is_not_in_motion_border since that's what it returns
3. The method TraceExtraction.save_metadata_to_db previously erroneously assumed the exclusion_label output file stored the exclusion labels as a list of strings for each roi under the format [{roi_id: 1, 'exclusion_label_name': ["name"]}, {roi_id: 2, 'exclusion_label_name': [}] However, it stores it as [{roi_id: 1, 'exclusion_label_name': "name_a"}, {roi_id: 1, 'exclusion_label_name': "name_b"}] The method and associated test assets are updated to reflect that.

[mikejhuang]

Confirmed yesterday's discussion with unit tests where the ROI both touches and crosses each of the 4 borders (left, right, top, bottom). With the erroneous -1 added, the roi touching the right and bottom is detected as being part of the motion border. With the -1 removed, it behaves consistently with all 4 sides.