feat(uglify): move uglify to external plugin from webpack-contrib

[TheLarkInn]

What kind of change does this PR introduce?
Refactoring

Did you add tests for your changes?
N/A

If relevant, link to documentation update:

Summary
This PR removes uglifyjs as a direct dependency and removes the internal uglifyjsplugin reference and points it to uglifyjs-webpack-plugin

This allows a bit more freedom to work, change, (or remove later) the uglifyjs-webpack-plugin in a much faster pace (in the case something downstream is breaking).

Does this PR introduce a breaking change?
No

Other information
N/A

[sokra]

webpack-sources dependency in uglifyjs plugin need to be updated

[TheLarkInn]

Thanks I'll grab and leave this open and update.

[michael-ciniawsky]

Will this supersede #5010 ? UgilfyJSPlugin is still coupled to core here to some point, I additionally removed optimize-minimize in #5010, which might b a bit harsh tbh, but the reason is that neither this.minimize (Loader API [deprecated]) nor UgilfyJSPlugin should have special meaning anymore as I understood :)

[bebraw]

Maybe add a deprecation note if used through webpack itself.

[TheLarkInn]

I'll get to this today

[sokra]

yarn.lock file need to be updated when plugin was updated

[webpack-bot]

@TheLarkInn Thanks for your update.

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

@sokra Please review the new changes.

[webpack-bot]

Thank you for your pull request! The most important CI builds succeeded, we’ll review the pull request soon.

[sokra]

Thanks