Replace manual checkbox labeling with CheckboxListTile

[doctor-g]

Right now, the settings screen manually connects a Checkbox with a TextButton. Reviewing the documentation reveals that CheckboxListTile does exactly that, so it should be used instead.

[doctor-g]

Looking more into this, CheckboxListStyle always puts the checkbox on the right, but this would be awkward for specifying the quests at the very least. A better approach is explained by the CheckboxListStyle documentation: to make a custom combination of widgets to show the checkbox on the left and text on the right. This will be functionally equivalent to the current code, but it would remove some of the unnecessary redundancy.