Captchas are not rendered anymore.

[LKS90]

With one of the recent core changes, it seems that the captcha elements are no longer rendered.
Every assertCaptchaPresence() call fails in the tests and when enabling the module and placing a captcha somewhere, one can confirm it as well.

[LKS90]

It seems like most of the theming functions aren't actually called anymore? I'll try and create a CaptchaElement that extends FormElement, maybe that's enough so the captcha is suddenly rendered again.