Have the toolbar button change to indicate that rulesets were applied or H-E is disabled

I suspect that there is a UI discoverability problem with the toolbar button: it currently doesn't do a good job of telling you that you can see what rulesets were applied to a page. The result is bugs like #4869 (moved).

If the toolbar button changed when rulesets were applicable, similar to the way that the NoScript context menus do, that would help!