Add force_public_test_summary and make failed public tests display correctly

[chrispyles]

Closes #539

[codecov]

Codecov Report

Base: 72.84% // Head: 73.15% // Increases project coverage by +0.30% 🎉

Coverage data is based on head (015e590) compared to base (47f008a).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #549      +/-   ##
==========================================
+ Coverage   72.84%   73.15%   +0.30%     
==========================================
  Files          62       62              
  Lines        3742     3747       +5     
==========================================
+ Hits         2726     2741      +15     
+ Misses       1016     1006      -10     

Impacted Files	Coverage Δ
otter/run/run_autograder/autograder_config.py	100.00% <100.00%> (ø)
otter/test_files/__init__.py	65.98% <100.00%> (+3.74%)	⬆️
otter/run/run_autograder/runners/python_runner.py	85.86% <0.00%> (+6.52%)	⬆️

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