refactor(plugin-webpack): cleanup

[malept]

• I have read the contribution documentation for this project.
• I agree to follow the code of conduct that this project follows, as appropriate.
• The changes have sufficient test coverage (if applicable).
• The testsuite passes successfully on my local machine (if applicable).

Summarize your changes:

Follow-up from #2225:

• Code refactors for clarity
• Removes the webpack-dev-server test, because it caused the testsuite to process.exit() early. This will likely be rewritten after feat(plugin-webpack): improve native asset relocation without forking Vercel loader #2320 lands since it has better support for webpack-based integration tests.

[codecov]

Codecov Report

Merging #2368 (5a81430) into master (84aaa8c) will decrease coverage by 0.80%.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master    #2368      +/-   ##
==========================================
- Coverage   75.57%   74.77%   -0.81%     
==========================================
  Files          74       76       +2     
  Lines        2203     2287      +84     
  Branches      416      434      +18     
==========================================
+ Hits         1665     1710      +45     
- Misses        421      472      +51     
+ Partials      117      105      -12     

Impacted Files	Coverage Δ
packages/plugin/webpack/src/WebpackPlugin.ts	33.87% <0.00%> (-24.60%)	⬇️
packages/plugin/webpack/src/WebpackConfig.ts	97.61% <100.00%> (ø)
packages/utils/web-multi-logger/src/Log.ts	0.00% <0.00%> (-100.00%)	⬇️
packages/utils/web-multi-logger/src/Logger.ts	21.05% <0.00%> (-68.43%)	⬇️
packages/utils/web-multi-logger/src/Tab.ts	20.00% <0.00%> (-60.00%)	⬇️
...es/plugin/webpack/src/util/ElectronForgeLogging.ts	13.79% <0.00%> (-48.28%)	⬇️
...lisher/electron-release-server/src/PublisherERS.ts	27.27% <0.00%> (ø)
packages/publisher/github/src/util/github.ts	100.00% <0.00%> (ø)
packages/template/base/src/determine-author.ts	100.00% <0.00%> (+17.64%)	⬆️
... and 7 more

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