Content blockers screen does not indicate "in progress" state

[ameshkov]

AdGuard should show a "loader" icon when the rules are being converted & registered by the content blocker. Once this is finished and Safari indicated that the content blocker is fully loaded, the icon should change to the green checkmark.

This behavior is observed all the time. While launching the application in version 1.9.13 and 14 Beta.

https://user-images.githubusercontent.com/62497891/119264002-a5491d00-bbe1-11eb-94dc-fbbf8f0f4dd8.mp4

Originally posted by @Oleg-Chashko in https://github.com/AdguardTeam/AdGuardForSafari/issues/600#issuecomment-846570663