feat: assume a closed pr with no osc label is internal #276

[nedbat]

This lets us close ex-edXers' pull requests without accidentally labelling them and adding them to projects.

This changes existing behavior: previously the bot was written to be able to first encounter PRs in their closed state. This change assumes all pull requests have been processed first when they are opened.

This PR includes #283, you can review them together or separately.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (3ee0182) 90.04% compared to head (15e0f1b) 89.76%.
Report is 3 commits behind head on master.

Files	Patch %	Lines
openedx_webhooks/tasks/pr_tracking.py	96.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #284      +/-   ##
==========================================
- Coverage   90.04%   89.76%   -0.29%     
==========================================
  Files          38       38              
  Lines        2853     2882      +29     
  Branches      398      397       -1     
==========================================
+ Hits         2569     2587      +18     
- Misses        259      268       +9     
- Partials       25       27       +2     

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