i18n: Localize label attribute of additional blocks

[bph]

Summary

Extends the "Localize Text" feature so that the label attribute of five more core blocks is wrapped in esc_attr_e() on theme save:

• core/navigation-link
• core/navigation-submenu
• core/home-link
• core/social-link
• core/categories

Each is added as a fall-through case in CBT_Theme_Locale::get_localizable_block_attributes() (includes/create-theme/theme-locale.php) alongside the existing label-only blocks. No new mechanism, no behavioural change for blocks already covered.

This continues the band-aid approach acknowledged in #776 — the architectural fix is tracked there.

Refs #825 (one part of it; core/file downloadButtonText / fileName will be a separate PR since those need rich-text/HTML handling).

Caveat for navigation blocks

Navigation menus stored as wp_navigation posts live outside templates and are not affected by this change. The fix only helps when a Navigation block contains inline navigation-link / navigation-submenu / home-link children in the template markup.

Test plan

• npm run lint:php — clean
• npm run test:unit:php — verified by CI (PHP 7.4 / 8.0 / 8.1 / 8.2 / 8.3, current and previous WP major).
• Manual smoke in WordPress Studio: ran the production pipeline (parse_blocks → escape_text_content_of_blocks → serialize_blocks → escape_block_attribute_strings) on hand-crafted markup for each of the five new blocks. All five produced the expected <?php esc_attr_e('<label>', '<theme-slug>');?> wrapping.