Allow TLA for legacy build and remove static Intl polyfills

[steverep]

Proposed change

Webpack's issue with TLA having ES5 support, webpack/webpack#11874, is likely never to get fixed, so I wrote a fairly simple plugin to do the job using Babel: https://github.com/steverep/transform-async-modules-webpack-plugin.

So this change gets rid of the static imports for the Intl polyfills, and now technically allows any TLA use. However, that comes with a big hiccup for now. Note that even though the change removes ~2MB of locale and time zone data from the bundle, the bundle size actually goes significantly up.

this is because the plugin does not make use of @babel/runtime and instead includes the helpers and regenerator inline. Because of duplicates from code splitting and the fact that every module that imports the polyfill is affected, that results in a lot of bytes. (Recall the drastic reductions from #16466.)

I think I can make the plugin use @babel/runtime, but it makes it much more complex. I could probably also mess with Webpack settings to reduce that duplication in a follow up. I think it's probably still worth merging now for browsers at the top of the legacy spectrum though since there would still be deferral benefits and some polyfill chunks would never get loaded.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue or discussion:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

[bramkragten]

Nice! 🚀

[steverep]

Took me like an hour just to fix the conflict because all my GPG keys expired 😮‍💨

[steverep]

re: your confusion... couldn't sign my commits