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 file header for wp-admin/install-helper.php
* Add markdown formatting and two inline `@see` tags to the description for `translate()`
* Markdown-indent a code snippet in the description for `_n_noop()`
* Remove HTML tags from the summary for `get_media_embedded_in_content()`
* Remove an HTML tag from the summary for `wpview_media_sandbox_styles()`

Props rarst.
See #30473.

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