Filtering in Admin UI crashes on some RegEx-specific characters ("(", "\", etc)

[jacobwod]

Typing a character in any filter field in Admin UI that can be interpreted as a valid modifier in a RegEx will lead to this crash:

The reason is that we seem to use the typed string directly as a regex expression, without previous sanitising. This should be fixed. Perhaps we don't need to use regular expressions at all anymore, for this very basic use case.