Unnecessary rewrite rules added for the /embed endpoint

[johnbillion]

WordPress appends /embed to a bunch of rewrite rules that it shouldn't. By default, the following rewrite rules are present on every site but are not valid:

• category/(.+?)/embed/?$
• tag/([^/]+)/embed/?$
• type/([^/]+)/embed/?$
• comments/embed/?$
• search/(.+)/embed/?$
• author/([^/]+)/embed/?$
• ([0-9]{4})/([0-9]{1,2})/([0-9]{1,2})/embed/?$
• ([0-9]{4})/([0-9]{1,2})/embed/?$
• ([0-9]{4})/embed/?$
• [0-9]{4}/[0-9]{1,2}/[^/]+/([^/]+)/embed/?$

These are generated in WP_Rewrite::generate_rewrite_rules().

Related: #35067

[swissspidy]

See also #35567 for supporting embeds for other object types