Formatting: Prevent wp_slash from returning non-strings as strings.

If a bool/float/int is passed into wp_slash it will be coerced into a string.

This changes the behavior to only slash strings. At the same time, handles recursion a little nicer by calling array_map for arrays.

Fixes #42195, #24106.

Props johnbillion, andizer, jrf, ryotasakamoto, SergeyBiryukov, donmhico, TobiasBg, markoheijnen, ryan, nacin, devesine, whyisjake.


Built from https://develop.svn.wordpress.org/trunk@48433


git-svn-id: https://core.svn.wordpress.org/trunk@48202 1a063a9b-81f0-0310-95a4-ce76da25c4cd