refactor: migrate configtest package to ESM

[snitin315]

What kind of change does this PR introduce?
refactor.

Did you add tests for your changes?
No
If relevant, did you update the documentation?
No
Summary
Start ESM migration.

Does this PR introduce a breaking change?
No

Other information
No

[evenstensberg]

Maybe draft these ESM converted packages and group them up, until every package is done migrated?

[snitin315]

Yes, I'll convert this to a draft.

[alexander-akait]

@snitin315 I think in this PR we need to convert all to ESM (or alternative we can use import(...)) to load extensions for webpack-cli, so they will work

[codecov]

Codecov Report

Merging #3439 (f2eb1eb) into next (f2eb1eb) will not change coverage.
The diff coverage is n/a.

❗ Current head f2eb1eb differs from pull request most recent head e0737fe. Consider uploading reports for the commit e0737fe to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             next    #3439   +/-   ##
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  Coverage   84.82%   84.82%           
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  Files          22       22           
  Lines        1588     1588           
  Branches      447      447           
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  Hits         1347     1347           
  Misses        241      241           

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[snitin315]

@alexander-akait I suppose if we move to ESM it will break compatibility with webpack v5 too. Because webpack 5 is using cli with require

[alexander-akait]

@snitin315 What about if we will use import(...)? It should work

[snitin315]

@alexander-akait yes but it means from webpack v5.0.0 to the current latest version of webpack will not work with this major version. It will be compatible only with future version of webpack which is using import().

[alexander-akait]

Hm, I cannot undestand... Webpack can have any type - commonjs or ESM, we just load it using import(...) and reuse, if you want to use ESM package in commonjs - just use import(...)... it is the official working solution

[snitin315]

@alexander-akait Yes import(...) will work. But it means users will have to update webpack to the latest version which includes this PR webpack/webpack#16448

[alexander-akait]

@snitin315 Oh, I got it, yeah, let's postpone it then, and mark it for webpack v6, we will need to do it for webpack-dev-server too

[snitin315]

@alexander-akait yes, let's postpone.

[alexander-akait]

Let's close in favor #3436, I think we will start migration everywhere on ESM when Node.js@18 will be outdated, because there are some bugs in Node.js@18 with ESM and especial with import(...), we can make a pain for many developers if we do it right now, anyway thank you