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.