executors: fully type every single executor

[kiritofeng]

Supersedes #951.

[codecov-commenter]

Codecov Report

Attention: 43 lines in your changes are missing coverage. Please review.

Comparison is base (e44898f) 81.30% compared to head (06e9043) 81.26%.
Report is 1 commits behind head on master.

Files	Patch %	Lines
dmoj/executors/COFFEE.py	0.00%	11 Missing ⚠️
dmoj/executors/TUR.py	57.14%	6 Missing ⚠️
dmoj/executors/D.py	33.33%	4 Missing ⚠️
dmoj/executors/SWIFT.py	33.33%	4 Missing ⚠️
dmoj/executors/GROOVY.py	88.88%	3 Missing ⚠️
dmoj/executors/RUBY.py	82.35%	3 Missing ⚠️
dmoj/executors/SCALA.py	86.95%	3 Missing ⚠️
dmoj/executors/BASH.py	0.00%	2 Missing ⚠️
dmoj/executors/KOTLIN.py	89.47%	2 Missing ⚠️
dmoj/executors/OBJC.py	75.00%	2 Missing ⚠️
... and 2 more

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1147      +/-   ##
==========================================
- Coverage   81.30%   81.26%   -0.05%     
==========================================
  Files         141      141              
  Lines        5028     5342     +314     
==========================================
+ Hits         4088     4341     +253     
- Misses        940     1001      +61     

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