Don't show browser extension alert if it's already installed

Created by: felixfbecker

Fixes #14560

@tjkandala I tried to move the logic more into one place, replace useState() with derived expressions and use useLocalStorage(). With some logic I wasn't sure though for the popover so please take a close look (small feedback: some more comments/docblocks would have helped).

I also improved the detection of the Chrome extension when it doesn't have permissions (i.e. on private instances).