Use shared Babel.js configuration

[francoisfreitag]

Keep in sync with other repositories by using the centralized
configuration for Babel.js.

[francoisfreitag]

I regenerated the JS and source map files after the config change, hopefully that’ll make the Node build green.

[francoisfreitag]

Figured it out, I had make watch-js running in another tab 🤦.

[francoisfreitag]

I do not understand what is going on yet, but it is due to the switch from modules: false to modules: 'commonjs'.
I can reproduce the failure locally, will get more familiar with the karma test setup and hopefully report back within a few days.

[francoisfreitag]

Changing the config is a large change.

Previously, because module was false, the “compiled” JavaScript could execute directly in the global context. When modules is set to 'commonjs', the scripts are limited to their own module. The globals should likely be registered through the ProvidePlugin.
I’ll investigate how large of a change that is and report back.

[skjnldsv]

I do not understand what is going on yet, but it is due to the switch from modules: false to modules: 'commonjs'.
I can reproduce the failure locally, will get more familiar with the karma test setup and hopefully report back within a few days.

Ah, yes, unfortunately our test suite might not be compatible with our babel config. It's not a trivial change.
I started addressing this in #23973, but it's a mess.