feat: configtest validate default configuration

[alexander-akait]

What kind of change does this PR introduce?

feature

Did you add tests for your changes?

Yes

If relevant, did you update the documentation?

Yes

Summary

configtest wroks without config-path (loaded default webpack.config.[ext])

Does this PR introduce a breaking change?

No

Other information

No

[snitin315]

Need CI fix

[codecov]

Codecov Report

Merging #2354 (39dd318) into master (38869d2) will increase coverage by 0.20%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2354      +/-   ##
==========================================
+ Coverage   69.27%   69.47%   +0.20%     
==========================================
  Files          47       47              
  Lines        2099     2110      +11     
  Branches      536      541       +5     
==========================================
+ Hits         1454     1466      +12     
+ Misses        645      644       -1     

Impacted Files	Coverage Δ
packages/configtest/src/index.ts	96.66% <100.00%> (+1.92%)	⬆️
packages/webpack-cli/lib/webpack-cli.js	90.85% <100.00%> (ø)
packages/webpack-cli/lib/utils/logger.js	88.88% <0.00%> (+11.11%)	⬆️

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