docs: add missing null to $post param types

[apermo]

Several functions across core accept null as a valid value for their $post parameter ($post = null in the function signature), but the @param type annotation does not include null.

This patch adds null to the @param type for all affected functions across 9 files, and reorders wp_force_plain_post_permalink() from WP_Post|int|null to the conventional int|WP_Post|null.

Changes

• general-template.php: get_the_date, get_the_modified_date, get_the_time, get_post_time, get_post_datetime, get_the_modified_time, get_post_modified_time, get_post_timestamp
• comment-template.php: _get_comment_reply_id
• embed.php: get_post_embed_url, get_post_embed_html
• post.php: get_post_mime_type
• post-template.php: get_the_excerpt, post_class, get_post_class, get_page_template_slug
• category-template.php: has_category, has_tag, has_term
• ms-blogs.php: _update_posts_count_on_transition_post_status
• class-wp-widget-media.php: display_media_state
• link-template.php: wp_force_plain_post_permalink (type reorder)

Trac ticket: https://core.trac.wordpress.org/ticket/64645

Use of AI Tools

Used Claude Code to identify all locations of the missing phpdoc and to help with summarizing the changes. Every change was monitored and reviewed by myself before opening the PR.

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This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

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[github-actions]

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[github-actions]

A commit was made that fixes the Trac ticket referenced in the description of this pull request.

SVN changeset: 61649
GitHub commit: eef6fb2

This PR will be closed, but please confirm the accuracy of this and reopen if there is more work to be done.