Add dart format check to CI workflow

[danrmiller]

CI already fails so merging this won't make things any worse. The intent is that we run everything through dart format, commit the results, then going forward this check will fail if a file is changed by dart format.

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.84%. Comparing base (1139770) to head (d9f2dc0).
⚠️ Report is 1596 commits behind head on staging.
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Additional details and impacted files

@@             Coverage Diff              @@
##           staging    #1242       +/-   ##
============================================
+ Coverage     5.36%   56.84%   +51.48%     
============================================
  Files          797       28      -769     
  Lines        75915     1117    -74798     
============================================
- Hits          4075      635     -3440     
+ Misses       71840      482    -71358     

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