Plugins: Use centralized API to display information about updating PHP when a plugin requires a higher version.

This changeset uses the API functions introduced in [44476] to link to the resource about updating PHP when highlighting a plugin's required PHP version is not met. It furthermore expands them, introducing a new `wp_update_php_annotation()` function that prints the markup to indicate that the default URL has been altered by the web host, allowing it to be reused universally.

Furthermore, this changeset adds missing `update_php` capability checks before displaying the information about updating PHP.

Props afragen.
Fixes #45986. See #43986, #45686.


git-svn-id: https://develop.svn.wordpress.org/trunk@44627 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/functions.php

@@ -6716,3 +6716,28 @@ function wp_get_update_php_url() {
 function wp_get_default_update_php_url() {
 	return _x( 'https://wordpress.org/support/update-php/', 'localized PHP upgrade information page' );
 }
+
+/**
+ * Prints the default annotation for the web host altering the "Update PHP" page URL.
+ *
+ * This function is to be used after {@see wp_get_update_php_url()} to display a consistent
+ * annotation if the web host has altered the default "Update PHP" page URL.
+ *
+ * @since 5.1.0
+ */
+function wp_update_php_annotation() {
+	$update_url  = wp_get_update_php_url();
+	$default_url = wp_get_default_update_php_url();
+
+	if ( $update_url === $default_url ) {
+		return;
+	}
+
+	echo '<p class="description">';
+	printf(
+		/* translators: %s: default Update PHP page URL */
+		__( 'This resource is provided by your web host, and is specific to your site. For more information, <a href="%s" target="_blank">see the official WordPress documentation</a>.' ),
+		esc_url( $default_url )
+	);
+	echo'</p>';
+}