Symfony version(s) affected: 4.4.16

Description
StringUtil::trim() is doing preg_replace('/^[\pZ\p{Cc}]+|[\pZ\p{Cc}]+$/u', '', $string) to trim strings, however this regex is missing ZERO WIDTH SPACE (\xE2\x80\x8B) characters.

How to reproduce
http://sandbox.onlinephpfunctions.com/code/5b72e8ff76c34a313c0f2799995f56e5993b6b60

Possible Solution

p{Cf} catches this character, but it also catches some soft-hyphen (https://en.wikipedia.org/wiki/Unicode_character_property). I don't think that should be a problem though.

I suggest the regex to be changed to preg_replace('/^[\pZ\pC]+|[\pZ\pC]+$/u', '', $string).
Cc and Cf are the only categories with characters in the C group anyway.