feat: default to core-js version 3

[danielroe]

Types of changes

• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

This PR upgrades the Nuxt core-js dependency to v3. Users can still opt-in to old core-js@2 version if they want by installing the package at root-level, although this is not advised.

warning core-js@2.6.12: core-js@<3.3 is no longer maintained and not
recommended for usage due to the number of issues. Because of the V8
engine whims, feature detection in old core-js versions could cause
a slowdown up to 100x even if nothing is polyfilled. Please, upgrade
your dependencies to the actual version of core-js.

closes #9851

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly. (PR: #)
• I have added tests to cover my changes (if not applicable, please state why)
• All new and existing tests are passing.

[codecov-commenter]

Codecov Report

Merging #9987 (ad09d74) into dev (4bf7c35) will not change coverage.
The diff coverage is 50.00%.

@@           Coverage Diff           @@
##              dev    #9987   +/-   ##
=======================================
  Coverage   65.10%   65.10%           
=======================================
  Files          94       94           
  Lines        4155     4155           
  Branches     1172     1172           
=======================================
  Hits         2705     2705           
  Misses       1171     1171           
  Partials      279      279           

Flag	Coverage Δ
unittests	65.10% <50.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
packages/webpack/src/config/base.js	65.89% <50.00%> (ø)

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[gkatsanos]

hey @danielroe / @pi0 I guess we'll see this one in the next nuxtjs release? (do we have an estimate of when will that be? )

[pi0]

@gkatsanos You can use nuxt-edge with a pinned version in the meantime.

[gkatsanos]

Hello @pi0 is this released or not yet?

[rchl]

I'm not sure if it's stated anywhere, if so then I apologize, but core-js needs to be in project's dependencies for everything to work properly (it's required for server middleware, depending on what constructs are used there).

I'm not sure if that was also the case with core-js 2x. If so then it's not technically a breaking change, but I feel that the fact that core-js needs to be installed as a prod dependency should be mentioned somewhere. Possibly even enforced with some runtime hook or something.

[rchl]

Also, maybe (depending on what what was the initial reasoning) this should be removed now:

https://github.com/nuxt/nuxt.js/blob/a10e5dd49fc06dc8b9e2a8983b10f2d025ad7328/renovate.json#L9-L9

?