Figure out a more reliable way of mapping tabs on browser startup

[bitspook]

Firefox resets the tabIds when it restarts. So we use org-ids for identifying
saved tabs. This works once the browser is up and running, since all the tabs
are kept in sync (unless user manually unchains a tab, in which case we don't
updated saved entry).

One solution for this can be keeping a local storage of tabs and their saved
IDs. But that has a small challenge as well; MDN recommends that we don't use
localStorage, but storage.local is extension wide; not tab local.

Besides, I am not sure how big a problem this is going to be. I am parking this
issue here as a documentation of this behavior. We'll pick it up when and if we
want it solved.