Bug 1624269 - P2. Cache access granted result in the 3rd-party window instead of top-level window in fission mode. r=timhuang,baku

Before this patch, in non-fission mode, we cache storage access granted result
in the top-level window so we don't have to iterate all the browsing contexts
in the same tree while syncing the storage permission granted decision.

However, since we plan to rely on the current update mechanism to sync
mHasStorageAccess flag for different documents in the same tab (instead of using
the syncing mechanism of permission manager), we will eventually need to iterate
the browsing context tree to find all the documents to sync. Base on this,
we no longer have to maintain different method for fission and non-fission.

In this patch, we store the permission granted result in the inner
window instead of using permission key and store the key in the top-level
window.

Differential Revision: https://phabricator.services.mozilla.com/D73710