Shortcodes: Make sure `wp.shortcode.string()` accepts the `attrs` array keys in any order.

Props yale01, georgestephanis, adamsilverstein, zsusag, mircoraffinetti, SergeyBiryukov.
Fixes #36263.
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git-svn-id: https://core.svn.wordpress.org/trunk@46803 1a063a9b-81f0-0310-95a4-ce76da25c4cd