GafferUI.PresetsPlugValueWidget: label does not support all special characters

[nikos3d]

Version: Gaffer 1.5.16.1-linux

Description

The GafferUI.PresetsPlugValueWidget doesn't support all special characters in the label field. This means that if you for example want to display Light Path Expressions that heavily utilise the * or [ characters, the output isn't shown correctly.

Steps to reproduce

1. Add a new user string plug on any node.
2. Open the UI Editor and change the widget of this plug to "Presets Menu"
3. Hit + and add a new entry containing the special characters "*" or "[".
4. Note how the wildcard and open brackets change to an underscore in the label field.