Editor: Add support for text inputs to theme.json.

Adds support for text input elements to theme.json so that theme builders and extenders can be style text input elements consistently.

Text input elements are `textarea`, and `input` with type `email`, `number`, `password`, `search`, `text`, `tel` and `url`. We are targeting the HTML elements directly rather than adding a CSS class, as we do for other elements that theme.json supports. This commit adds no extra styling unless a theme opts in to use this and the specificity of any generated CSS with the element is 0.

See original Gutenberg PR: WordPress/gutenberg#70378.

Example usage:

{{{
	"elements": {
		"textInput": {
			"border": {
				"radius": "0",
				"style": "solid",
				"width": "1px",
				"color": "red"
			},
			"color": {
				"text": "var(--wp--preset--color--theme-2)"
			},
			"typography": {
				"fontFamily": "var(--wp--preset--font-family--inter)"
			}
		}
	}
}}}

Reviewed by mukesh27, scruffian.
Merges [9600] to the 6.9 branch.

Props onemaggie, mukesh27, sabernhardt, joen, get_dave, wildworks, ocean90, mikachan, poena.
Fixes #63878. See #63555.

git-svn-id: https://develop.svn.wordpress.org/trunk@61023 602fd350-edb4-49c9-b593-d223f7449a82

Author: scruffian

src/wp-includes/class-wp-theme-json.php

@@ -613,22 +613,24 @@ class WP_Theme_JSON {
 	 *
 	 * @since 5.8.0
 	 * @since 6.1.0 Added `heading`, `button`, and `caption` elements.
+	 * @since 6.9.0 Added `textInput` elements.
 	 * @var string[]
 	 */
 	const ELEMENTS = array(
-		'link'    => 'a:where(:not(.wp-element-button))', // The `where` is needed to lower the specificity.
-		'heading' => 'h1, h2, h3, h4, h5, h6',
-		'h1'      => 'h1',
-		'h2'      => 'h2',
-		'h3'      => 'h3',
-		'h4'      => 'h4',
-		'h5'      => 'h5',
-		'h6'      => 'h6',
+		'link'      => 'a:where(:not(.wp-element-button))', // The `where` is needed to lower the specificity.
+		'heading'   => 'h1, h2, h3, h4, h5, h6',
+		'h1'        => 'h1',
+		'h2'        => 'h2',
+		'h3'        => 'h3',
+		'h4'        => 'h4',
+		'h5'        => 'h5',
+		'h6'        => 'h6',
 		// We have the .wp-block-button__link class so that this will target older buttons that have been serialized.
-		'button'  => '.wp-element-button, .wp-block-button__link',
+		'button'    => '.wp-element-button, .wp-block-button__link',
 		// The block classes are necessary to target older content that won't use the new class names.
-		'caption' => '.wp-element-caption, .wp-block-audio figcaption, .wp-block-embed figcaption, .wp-block-gallery figcaption, .wp-block-image figcaption, .wp-block-table figcaption, .wp-block-video figcaption',
-		'cite'    => 'cite',
+		'caption'   => '.wp-element-caption, .wp-block-audio figcaption, .wp-block-embed figcaption, .wp-block-gallery figcaption, .wp-block-image figcaption, .wp-block-table figcaption, .wp-block-video figcaption',
+		'cite'      => 'cite',
+		'textInput' => 'textarea, input:where([type=email],[type=number],[type=password],[type=search],[type=text],[type=tel],[type=url])',
 	);
 
 	const __EXPERIMENTAL_ELEMENT_CLASS_NAMES = array(