Enforce scalafmt across the full codebase

[pomadchin]

We tried to keep the changes minimal but it turned out to be of a harder maintenance.

cc @cchantep / @imarios

linked #726
closes #939

[codecov]

Codecov Report

❌ Patch coverage is 95.51020% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 95.67%. Comparing base (64b6a3c) to head (8d14d35).
⚠️ Report is 30 commits behind head on master.

Files with missing lines	Patch %	Lines
...taset/src/main/scala/frameless/RecordEncoder.scala	93.58%	5 Missing ⚠️
cats/src/main/scala/frameless/cats/implicits.scala	0.00%	3 Missing ⚠️
...ore/src/main/scala/frameless/CatalystOrdered.scala	93.33%	1 Missing ⚠️
...taset/src/main/scala/frameless/functions/Udf.scala	85.71%	1 Missing ⚠️
...rameless/ml/regression/TypedLinearRegression.scala	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #944      +/-   ##
==========================================
+ Coverage   95.46%   95.67%   +0.21%     
==========================================
  Files          67       68       +1     
  Lines        1257     1342      +85     
  Branches       42       48       +6     
==========================================
+ Hits         1200     1284      +84     
- Misses         57       58       +1     

Flag	Coverage Δ
2.12-root-spark33	?
2.12-root-spark34	95.69% <95.43%> (+0.23%)	⬆️
2.12-root-spark35	95.69% <95.43%> (?)
2.13-root-spark35	96.26% <96.21%> (+0.20%)	⬆️
2.13-root-spark40	96.21% <96.23%> (?)

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