Backport performance improvements of StringUtil::encodeEmail

[ausi]

I think we should backport contao/core-bundle@4d26b21 to fix the performance issues in Contao 3.5 too.

If we don’t want to backport the whole new email-handling, i think it is enough to replace the *s in StringUtil.php:305 with {1,64} and {1,252}.

The performance issue itself can be reproduced by executing \StringUtil::encodeEmail(str_repeat('x', 100 * 1024));;

[leofeyer]

Back ported in 682ab51.

[ausi]

I think I made a mistake, it should be {0,64} and {0,252}, otherwise ab@a.xx only matches as b@a.xx

[leofeyer]

Fixed in 4cfdfb4.