General: Add inline PHPCS options to leave regex indentation.

We have a handful of super long regexen that are written over multiple lines, as a collection of strings concatenated together. Each string is indented appropriately for the regex, but PHPCS doesn't recognised this, so defaults to removing the extra whitespace.

Disabling the `Squiz.Strings.ConcatenationSpacing.PaddingFound` rule for these blocks stops the extra whitespace from being removed.

See #41057.


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git-svn-id: https://core.svn.wordpress.org/trunk@42078 1a063a9b-81f0-0310-95a4-ce76da25c4cd