fix: resolve dev server hot options correctly

[anshumanv]

What kind of change does this PR introduce?
fix

Did you add tests for your changes?
Yes

If relevant, did you update the documentation?
Need update

Summary

• Fix how hot flag is resolved in serve package

Does this PR introduce a breaking change?
No

Other information
Fixes #2004

[alexander-akait]

Can we add simple test for webpack serve --hot and webpack serve --hot=only to avoid problems in future

[rishabh3112]

Left a suggestion. Rest looks good to me 😃

[anshumanv]

Can we add simple test for webpack serve --hot and webpack serve --hot=only to avoid problems in future

We already have tests for hot and no-hot flags, also updated the tests for createConfig which was causing this problem, adding for hot-only

[snitin315]

Need a rebase

[alexander-akait]

/cc @anshumanv can you rebase, I think we should do release today

[webpack-bot]

@anshumanv Thanks for your update.

I labeled the Pull Request so reviewers will review it again.

@snitin315 Please review the new changes.

[anshumanv]

rebase done

[codecov]

Codecov Report

Merging #2022 into master will increase coverage by 0.06%.
The diff coverage is 64.70%.

@@            Coverage Diff             @@
##           master    #2022      +/-   ##
==========================================
+ Coverage   68.99%   69.05%   +0.06%     
==========================================
  Files          85       85              
  Lines        2422     2443      +21     
  Branches      489      492       +3     
==========================================
+ Hits         1671     1687      +16     
- Misses        751      756       +5     

Impacted Files	Coverage Δ
packages/serve/src/parseArgs.ts	90.47% <0.00%> (-4.53%)	⬇️
packages/serve/src/startDevServer.ts	93.33% <ø> (+2.02%)	⬆️
packages/serve/src/index.ts	84.61% <66.66%> (-15.39%)	⬇️
packages/serve/src/createConfig.ts	64.70% <77.77%> (+9.15%)	⬆️

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[alexander-akait]

/cc @webpack/cli-team

Will be great to add more tests, but let's focus on coverage in other PRs