Ensure inline code is markdown-escaped as such, HTML tags are removed from summaries, and that code snippets in descriptions are properly indented.

Affects DocBlocks for the following core elements:
* Markdown-indent a code snippet in the description for `_deprecated_argument()`
* Markdown-indent a code snippet in the description for `wp_localize_script()`
* Backtick-escape HTML tags in two parameter descriptions for `wp_register()`
* Various DocBlock formatting in the description for `get_bloginfo()`
* Remove HTML tag from the summary for `_wp_render_title_tag()`
* Backtick-escape a HTML tag in the description for `get_archives_link()`
* Markdown-indent a code snippet in the description for `wp_admin_css_color()`
* Markdown-indent a code snippet in the description for the `welcome_panel` hook

Props rarst.
See #30473.


git-svn-id: https://develop.svn.wordpress.org/trunk@30541 602fd350-edb4-49c9-b593-d223f7449a82