This patch refactors the SearchService private initialized variables and how
the SearchService stores its initialization status. These changes capture whether
the SearchService has succeeded, failed or hasn't finished initialization yet.
There are also changes made to UrlbarSearchUtils on handling when SearchService
has failed to initialize or when it hasn't finished initializing yet and we wait.
In the case where the SearchService has failed on initialization, We allow
the code to continue so that it can reach UrlbarProviderPlaces. Once we
are able to reach UrlbarProviderPlaces, we can make database calls for the user's
history and bookmarks. This allows the user to interact with the addressbar and
search their history and bookmarks even if SearchService has failed to initialize.
Differential Revision: https://phabricator.services.mozilla.com/D176936
9864559021
