Fix #405 - Improve test stability and performance for popup blocking

This is a collection of a few smaller changes:

• Previously, when the service worker was suspended, we might lookup the same filter and remove a tab multiple times. This adds an early exit for that case where the filtering has already been done by a different event.
• The default popup opener is no longer opened before the sitekey allowlisting tests which don't use it. This is to save some time.
• Checking for a popup being blocked now has a tolerance. The popup is considered to have been blocked even if it does load, as long as it's closed within that tolerance. The tolerance is unfortunately high for service worker fuzz tests at the moment, but can only be improved by improving our overall startup time (also fixes #272 (closed)).
• Increased the default fuzz test timeout. Hopefully we can pull this down again with optimizing our startup performance in the future.
• Bump out selenium version to take advantage of any bugfixes on their side.
• Generalized the retry mechanism we already have if we hit certain selenium errors in low resource environments.