Theme.json: dynamic references, avoid recursive references

[MaggieCabrera]

Description

Pointed out in #42976, the editor crashes when there's a recursive reference in place.

Step-by-step reproduction instructions

In theme.json add:

"color": {
    "background": { "ref": "styles.color.text" },
    "text": {"ref": "styles.color.background" }
},

Screenshots, screen recording, code snippet

No response

Environment info

No response

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[ramonjd]

I have a fix for this. Just writing some tests and will push a PR soon.