Tech: make tests use SWC, not babel

[ndelangen]

Issue: #18732

Telescoped on: #20156

And now using SWC for transforming in jest

[tmeasday]

Wow, seems cool. So do we need to go back to using global vars for it/expect etc?

[ndelangen]

@tmeasday honestly, it's been a bit of an experimentation. Seeing how much babel stuff I could clean-up.

Good news is: It seems I can make all of it go away, pretty much!

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Because of the long list of telescoped PRs (trying to make smaller PRs that can be reviewed) I easily get into merge conflicts, and then try to fix them any way I can.

I suppose we should chat about these PRs and if we want them in 7.0 at all. If we decide we DO, I should start running all sandboxes on them, and get them merged 1 by 1, slowly and carefully.

[IanVS]

Any reason this needs to be telescoped onto the other PRs, and we shouldn't just commit it straight to next?

[ndelangen]

That sounds like a plan @IanVS!

It's probably not going to get the highest priority from me, since i only have a few more days until my trip.

This sounds like an easy contribution for someone to pick as their first contribution maybe?

General idea of the task:

• make a new branch based on next
• cherry pick the commits from the PR
• resolve conflicts
• make sure (unit) tests run & all pass
• submit PR with description

[ifndefdeadmau5]

May I take this one if anyone wouldn't mind? : )

[ndelangen]

closed in favor of #20397