[Runner JSON Output]: Changed Sort Order for Concept Exercises with Failed Subtests

[BethanyG]

1. Changed data.py to insert an ASCII sort signifier (~) for the parent of failed subtests in concept exercises.
2. Change the sort key(s) for concept exercises to sort the parent last in results.
3. Re-recorded the following golden test files for concept/task based test cases to account for new sort order:

• test/example-all-fail-tasks-and-subtests/results.json
• test/example-config-multiple-files-subtests-and-tasks/results.json
• test/example-has-stdout-and-tasks/results.json
• test/example-has-stdout-tasks-and-subtests/results.json
• test/example-partial-failure-with-subtests-and-stdout-2/example_partial_failure_with_subtests_and_stdout_2.py
• test/example-partial-failure-with-subtests-and-stdout-2/example_partial_failure_with_subtests_and_stdout_2_test.py
• test/example-partial-failure-with-subtests-and-stdout-2/results.json
• test/example-partial-failure-with-subtests-and-stdout/results.json
• test/example-partial-failure-with-subtests/results.json
• test/example-success-with-subtests/results.json