Prevent users from setting invalid wine prefixes

[arielj]

Problem description

We could have some validations for the prefix paths:

• make sure the directories are writable
• make sure the folder is not the game install folder
• I'm sure there are more cases we should prevent, having the setup to validate the prefix path will allow us to improve that in the future

Feature description

When a user changes a prefix directory, don't change the setting as the user types. Wait for the input to be burred and then run some validations, and only apply if the validations is successful. If it's not, let the user know with an error message (an allow to reset the value to the stored one)

Alternatives

Not sure, I guess not doing any validation.

Additional information

No response