"modal" dialogs for tabs aren't really modal

[bridiver]

some popover dialogs like basic auth appear to be modal, but will disappear and reappear if you navigate to other tabs using the keyboard shortcuts. We should either lock the browser to make them modal or attach them to the tabs somehow (watching out for potential spoofing issues)

[bsclifton]

Reworking the basic auth screen to work similar to the new alert/confirm should be pretty easy after #7107 is accepted 😄

[srirambv]

Windevine plugin prompt should be contained within the tab