Automatically generate required preset classes

[jorgefilipecosta]

This PR automatically generates the preset classes (colors, gradients, and font size) without requiring the theme to explicitly include the classes.

Required because on #25711 we are allowing the user to edit the color palette and in that case, we need to generate the classes for these colors. These change also makes things easier for theme developers.

How has this been tested?

I verified that the global-styles-inline-css style element now contains the classes fro the colors, font-sizes, etc.
I added the following date to lib/experimental-default-theme.json

	"core/button": {
		"settings": {
			"color": {
				"palette": [
					{
						"name": "White",
						"slug": "custom-white",
						"color": "#101010"
					}
				]
			}
		}
	}

And I verified the color classes scoped to the button were correctly generated.

[github-actions]

Size Change: +19 B (0%)

Total Size: 1.19 MB

Filename	Size	Change
build/block-library/index.js	145 kB	+19 B (0%)

ℹ️ View Unchanged

Filename	Size	Change
build/a11y/index.js	1.14 kB	0 B
build/annotations/index.js	3.52 kB	0 B
build/api-fetch/index.js	3.35 kB	0 B
build/autop/index.js	2.72 kB	0 B
build/blob/index.js	668 B	0 B
build/block-directory/index.js	8.55 kB	0 B
build/block-directory/style-rtl.css	943 B	0 B
build/block-directory/style.css	942 B	0 B
build/block-editor/index.js	130 kB	0 B
build/block-editor/style-rtl.css	11 kB	0 B
build/block-editor/style.css	11 kB	0 B
build/block-library/editor-rtl.css	8.65 kB	0 B
build/block-library/editor.css	8.65 kB	0 B
build/block-library/style-rtl.css	7.66 kB	0 B
build/block-library/style.css	7.65 kB	0 B
build/block-library/theme-rtl.css	741 B	0 B
build/block-library/theme.css	741 B	0 B
build/block-serialization-default-parser/index.js	1.78 kB	0 B
build/block-serialization-spec-parser/index.js	3.1 kB	0 B
build/blocks/index.js	47.6 kB	0 B
build/components/index.js	169 kB	0 B
build/components/style-rtl.css	15.5 kB	0 B
build/components/style.css	15.5 kB	0 B
build/compose/index.js	9.43 kB	0 B
build/core-data/index.js	12 kB	0 B
build/data-controls/index.js	685 B	0 B
build/data/index.js	8.6 kB	0 B
build/date/index.js	31.9 kB	0 B
build/deprecated/index.js	772 B	0 B
build/dom-ready/index.js	568 B	0 B
build/dom/index.js	4.42 kB	0 B
build/edit-navigation/index.js	10.6 kB	0 B
build/edit-navigation/style-rtl.css	868 B	0 B
build/edit-navigation/style.css	871 B	0 B
build/edit-post/index.js	306 kB	0 B
build/edit-post/style-rtl.css	6.29 kB	0 B
build/edit-post/style.css	6.28 kB	0 B
build/edit-site/index.js	20.9 kB	0 B
build/edit-site/style-rtl.css	3.73 kB	0 B
build/edit-site/style.css	3.73 kB	0 B
build/edit-widgets/index.js	21.2 kB	0 B
build/edit-widgets/style-rtl.css	3.02 kB	0 B
build/edit-widgets/style.css	3.02 kB	0 B
build/editor/editor-styles-rtl.css	492 B	0 B
build/editor/editor-styles.css	493 B	0 B
build/editor/index.js	45.5 kB	0 B
build/editor/style-rtl.css	3.85 kB	0 B
build/editor/style.css	3.84 kB	0 B
build/element/index.js	4.45 kB	0 B
build/escape-html/index.js	734 B	0 B
build/format-library/index.js	7.49 kB	0 B
build/format-library/style-rtl.css	547 B	0 B
build/format-library/style.css	548 B	0 B
build/hooks/index.js	1.74 kB	0 B
build/html-entities/index.js	621 B	0 B
build/i18n/index.js	3.54 kB	0 B
build/is-shallow-equal/index.js	710 B	0 B
build/keyboard-shortcuts/index.js	2.39 kB	0 B
build/keycodes/index.js	1.85 kB	0 B
build/list-reusable-blocks/index.js	3.02 kB	0 B
build/list-reusable-blocks/style-rtl.css	476 B	0 B
build/list-reusable-blocks/style.css	476 B	0 B
build/media-utils/index.js	5.13 kB	0 B
build/notices/index.js	1.69 kB	0 B
build/nux/index.js	3.27 kB	0 B
build/nux/style-rtl.css	671 B	0 B
build/nux/style.css	668 B	0 B
build/plugins/index.js	2.44 kB	0 B
build/primitives/index.js	1.34 kB	0 B
build/priority-queue/index.js	790 B	0 B
build/redux-routine/index.js	2.85 kB	0 B
build/rich-text/index.js	13 kB	0 B
build/server-side-render/index.js	2.6 kB	0 B
build/shortcode/index.js	1.7 kB	0 B
build/token-list/index.js	1.24 kB	0 B
build/url/index.js	4.06 kB	0 B
build/viewport/index.js	1.74 kB	0 B
build/warning/index.js	1.14 kB	0 B
build/wordcount/index.js	1.17 kB	0 B

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