refactor: use classes where applicable

[raphinesse]

Motivation and Context

This applies some of the changes contained in #112. For more information see #113.

Diffs are best reviewed by commit and ignoring whitespace changes.

Description

Applied lebab --replace src --transform class to the code and made some adjustments before and after.

Testing

Passes our test suite

[codecov-io]

Codecov Report

Merging #119 into master will decrease coverage by 0.55%.
The diff coverage is 89.87%.

@@            Coverage Diff             @@
##           master     #119      +/-   ##
==========================================
- Coverage   87.39%   86.83%   -0.56%     
==========================================
  Files          20       20              
  Lines        1491     1405      -86     
==========================================
- Hits         1303     1220      -83     
+ Misses        188      185       -3

Impacted Files	Coverage Δ
src/ActionStack.js	93.33% <100%> (-0.22%)	⬇️
src/ConfigChanges/ConfigKeeper.js	100% <100%> (ø)	⬆️
src/PluginInfo/PluginInfoProvider.js	82.14% <83.33%> (-1.73%)	⬇️
src/ConfigParser/ConfigParser.js	79.91% <83.87%> (-0.09%)	⬇️
src/PluginManager.js	88.63% <85.71%> (-3.04%)	⬇️
src/PlatformJson.js	79.22% <85.96%> (-3.2%)	⬇️
src/PluginInfo/PluginInfo.js	83.01% <86.36%> (-2.51%)	⬇️
src/ConfigChanges/ConfigFile.js	87.73% <88.46%> (-0.45%)	⬇️
src/ConfigChanges/ConfigChanges.js	94.64% <94.3%> (-0.33%)	⬇️

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