Section Styles: Fix ref values within block style variations

[aaronrobertshaw]

This PR backports the fix from:

• Section Styles: Resolve ref values in variations data gutenberg#63172

This restores the ability to reference style values from elsewhere within theme.json for block style variations.

Trac ticket: https://core.trac.wordpress.org/ticket/61589#ticket

Test Instructions

1. Add some ref values for block style variations to your theme.json e.g. update TT4 with the sections from the theme.json snippet below
2. Load the site editor and edit the default home page
3. Confirm that outline buttons are displayed and have the correct referenced style values
4. Save and ensure the same on the frontend

Example theme.json snippet

{
    "styles": {
        "elements": {
            "button": {
                "border": {
                    "color": "transparent",
                    "radius": "0.25em",
                    "style": "solid",
                    "width": "1px"
                },
                "color": {
                    "background": "var(--wp--preset--color--accent)",
                    "text": "var(--wp--preset--color--base)"
                },
                "spacing": {
                    "padding": {
                        "bottom": "0.5em",
                        "left": "1.25em",
                        "right": "1.25em",
                        "top": "0.5em"
                    }
                }
            }
        },
        "blocks": {
            "core/button": {
                "border": {
                    "color": { "ref": "styles.elements.button.border.color" },
                    "radius": { "ref": "styles.elements.button.border.radius" },
                    "style": { "ref": "styles.elements.button.border.style" },
                    "width": { "ref": "styles.elements.button.border.width" }
                },
                "color": {
                    "background": { "ref": "styles.elements.button.color.background" },
                    "text": { "ref": "styles.elements.button.color.text" }
                },
                "spacing": {
                    "padding": {
                        "bottom": { "ref": "styles.elements.button.spacing.padding.bottom" },
                        "left": { "ref": "styles.elements.button.spacing.padding.left" },
                        "right": { "ref": "styles.elements.button.spacing.padding.right" },
                        "top": { "ref": "styles.elements.button.spacing.padding.top" }
                    }
                },
                "variations": {
                    "outline": {
                        "border": {
                            "color": "currentColor",
                            "width": { "ref": "styles.elements.button.border.width" }
                        },
                        "color": {
                            "text": { "ref": "styles.elements.button.color.background" }
                        },
                        "spacing": {
                            "padding": {
                                "bottom": { "ref": "styles.elements.button.spacing.padding.bottom" },
                                "left": { "ref": "styles.elements.button.spacing.padding.left" },
                                "right": { "ref": "styles.elements.button.spacing.padding.right" },
                                "top": { "ref": "styles.elements.button.spacing.padding.top" },
                            }
                        }
                    }
                }
            }
        }
    }
}

Screenshots or screencast

Before	After

---

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

[github-actions]

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[andrewserong]

This is testing nicely for me, just as WordPress/gutenberg#63172 does on the site frontend. It'll need the JS packages update from that PR before it'll work in the site editor, but for the PHP changes this change looks good to land from my perspective!

[ramonjd]

I tested along the same lines as WordPress/gutenberg#63172

On the frontend, the values are being resolved from the theme.json tree as expected. 👍🏻

[github-actions]

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Core Committers: Use this line as a base for the props when committing in SVN:

Props aaronrobertshaw, andrewserong, ramonopoly.

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