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.

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