Blender Git Loki

Asset Browser: Improve hint for asset library that isn't found

We already show a message when showing an asset library whose path can't be
found on disk. The red text was making it look like some fatal error happened.
And the message could be a bit more useful generally.

So this removes the red color of the text, (arguably) improves the text and
adds a button as shortcut to open the Preferences with the asset library
settings.

Differential Revision: https://developer.blender.org/D12894