Formatting: In `sanitize_title_with_dashes()`, convert `&nbsp`, `&ndash`, and...

Formatting: In `sanitize_title_with_dashes()`, convert `&nbsp`, `&ndash`, and `&mdash` HTML entities to hyphens on save.

Props polevaultweb for initial patch.
Fixes #31790.
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git-svn-id: https://core.svn.wordpress.org/trunk@36742 1a063a9b-81f0-0310-95a4-ce76da25c4cd