standalone: update preset-stage-*

[sosukesuzuki]

Q	A
Fixed Issues?	N/A
Major: Breaking Change?	Y?
Minor: New Feature?	Y?
Tests Added + Pass?	Yes
License	MIT

I'm not sure that how we should treat this PR for semantic versioning.

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[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/47842/

[hzoo]

Yeah it's weird, we should mention we don't support stages https://babeljs.io/blog/2018/07/27/removing-babels-stage-presets since a few years ago it just happens to still be used as the api..

It's mostly for our own REPL, we should try to remove the feature entirely (just turn on all plugins or make it opt in like most people have to use it)

[nicolo-ribaudo]

Let's merge this as a minor.

For Babel 8, since everything will be ESM-based we might just consider dropping @babel/standalone support and relying on "exports" to differentiate between Node.js and browser code.

[existentialism]

👍 for minor

[JLHwung]

Removing stage 3 plugins is a breaking change. Because 'stage-3' no long enables the plugins that were enabled before Babel 7.15. We have to defer deletion to Babel 8. Otherwise this PR looks good to me.