Remove HTML `<head>` tags from DocBlock summaries in wp-admin/admin-header.php.

Also better-specify the `$hook_suffix` value in the `admin_head-$hook_suffix` hook docs per hook documentation precedent.

Props rarst for the initial patch.
See #30473

Built from https://develop.svn.wordpress.org/trunk@30535


git-svn-id: http://core.svn.wordpress.org/trunk@30524 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Ensure inline code is markdown-escaped as such, and that code snippets in descriptions are properly indented.

Affects DocBlocks for the following core elements:
* Two arguments in `_walk_bookmarks()`
* A code snippet in the class header for `WP_Roles`
* A code snippet in the class header for `WP_HTTP_Proxy`
* Inline code fixes in the summary and a parameter description for `WP_oEmbed::discover()`
* An argument description in `_WP_Editors::parse_settings()`
* Inline code fixes in the summary and a parameter description the `embed_oembed_discover` hook.

Props rarst.
See #30473.

Built from https://develop.svn.wordpress.org/trunk@30536


git-svn-id: http://core.svn.wordpress.org/trunk@30525 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Ensure inline code is markdown-escaped as such, and that code snippets in descriptions are properly indented.

Affects DocBlocks for the following core elements:
* Backtick-escapes a `<link>` tag in a parameter description for the `embed_oembed_discover` hook
* Inline code fixes in the summary and return description for `WP_List_Table::get_table_classes()`
* Removes HTML markup from the summary for `WP_List_Table::display_rows_or_placeholder()`
* Backtick-escapes a `<tr>` tag in a parameter description for `WP_Users_List_Table::single_row()`
* Converts non-DocBlocks into multi-line comments in `WP_Dependencies::do_items()`
* Removes HTML markup from the summary for the `comment_form_top` hook.
* Inline code and snippet fixes in the description for `wp_get_schedules()`

Props rarst for the initial patch.
See #30473.

Built from https://develop.svn.wordpress.org/trunk@30537


git-svn-id: http://core.svn.wordpress.org/trunk@30526 1a063a9b-81f0-0310-95a4-ce76da25c4cd