Avoid double hide/show calls on validation bubble

[mkhatib]

This to track avoiding calling hide or show when we're already at the exact same state that we'll end up with after the call. Following up on this PR discussion.

One last: We may end up double calling #hide and #show. Storing the current message as a state on ValidationBubble, we can check if we're already hidden, or if we're trying to show the same message again. In either case, we can return without doing anything.

Yeah we'd also need to store the targetElement and visibility state of the bubble in that state to make sure we're calling show for the same element as well.