Toolbar icon remains disabled after navigating to a nonallowlisted site

Environment

• OS version: /
• Browser version: reproducible in latest versions of FF, Chrome, Opera and Edge
• Extension version: next branch
• Last working version: ABP 3.12

Steps to reproduce

1. install the extension
2. go to www.example.com
3. open the popup and allowlist the website (observe that the toolbar icon is greyed out)
4. in the same window, navigate to to https://testpages.adblockplus.org/

Observed behavior

• toolbar icon remains greyed out
• if the page https://testpages.adblockplus.org/ is refreshed, or the user navigates to another page, the icon becomes enabled again (to indicate that adblocking is active)
• NOTE: adblocking continues to work, it's just that the icon is not updated

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Expected behavior

The toolbar should be in enabled state when adblocking is active.

Further information

N/A, I am just horribly terribly sorry that I only found this on the Friday afternoon before the release on Monday. 😞

Not sure if this really is an impediment, considering not many users have the icon pinned and the adblocking is not actually affected, but adding a label until it's decided otherwise.

This problem is caused by a change in behavior introduced by EWE, whereas the tab is not yet seen as "allowlisted" when the navigation has started, but only after the navigation was committed. Therefore we should wait for that to occur before determining the tab's allowlisting state.

Hints for testers

The extension no longer checks whether to show a server-side notification in response to the user navigating to a certain URL. This functionality was removed from the notification system in eyeo/adblockplus/abc/adblockpluscore#97 (closed), but we still unnecessarily checked for notifications on each navigation.