Localize Details block summary text

[t-hamano]

Part of #776

Testing Instructions

• Insert a Details block into one of the templates and enter summary text.
• Save the template.
• From the CBT sidebar, click the Save button.
• Verify that the localization function is applied to the Summary text.

Before

<?php
/**
 * Title: home
 * Slug: twentytwentyfive/home
 * Inserter: no
 */
?>
<!-- wp:details -->
<details class="wp-block-details"><summary>Details Summary</summary><!-- wp:paragraph {"placeholder":"Type / to add a hidden block"} -->
<p><?php esc_html_e('Details Content', 'twentytwentyfive');?></p>
<!-- /wp:paragraph --></details>
<!-- /wp:details -->

After

<?php
/**
 * Title: home
 * Slug: twentytwentyfive/home
 * Inserter: no
 */
?>
<!-- wp:details -->
<details class="wp-block-details"><summary><?php esc_html_e('Details Summary', 'twentytwentyfive');?></summary><!-- wp:paragraph {"placeholder":"Type / to add a hidden block"} -->
<p><?php esc_html_e('Details Content', 'twentytwentyfive');?></p>
<!-- /wp:paragraph --></details>
<!-- /wp:details -->