Further improve #52150

What problem does this address?

#52150 aims to expose the Site Editor Patterns page for every "theme".

However, currently the Site Editor is only accessible to admin users. For non-admin users, links related to the Pattern page link to the classic post list (edit.php?post_type=wp_block).

What is your proposed solution?

We should be able to remove this restriction and allow all users to access the Site Editor Patterns page.

To achieve this, I think we need to implement at least the following points:

• Even if the current theme is a block theme, non-admin users are not allowed to access anything other than the Patterns page.
• Check capabilities to restrict actions such as creating, duplicating, deleting, and editing patterns. The "wp_block" post type has complex capabilities.
• Implement redirects in case the post list page is bookmarked or the post list page is hard-coded by third-party product developers.