KSES: Make the URI attributes DRY.

This commit introduces the `wp_kses_uri_attributes` function and filter. The function centralizes the list of attributes, in order to prevent inconsistency, and the filter provides a way for plugins to customize the attributes.

Merges [44014] and [44017] to `trunk`.

Built from https://develop.svn.wordpress.org/trunk@44207


git-svn-id: https://core.svn.wordpress.org/trunk@44037 1a063a9b-81f0-0310-95a4-ce76da25c4cd