Don't restrict regions for paid WiP - Don't merge yet - this has deps

This is a branch to remove the restrictions for addon exclusion records for paid apps.

This requires a bunch of changes ahead of this branch to be possible namely:

* Having the search index deal with whether apps should be shown based on region or not
* Having the search index be updated for all apps affected by price changes / price regions being turned off etc.
* Checking the way featured apps are surfaces so that pricing data is taken into account.

These will all be done ahead of this branch landing in other branches.

This branch makes the regions the user can be excluded from independent to the price region data so we're not trying to amend the exclusion records based on what price the user has selected. Doing this makes it easier to enable the users' app in the new regions when they have payments enabled (assuming relevant to the price).

This change also makes use of a new field for whether the app should be automatically enabled for new regions. This is instead of using worldwide to track this so we have the same field for both free and paid apps. In both cases worldwide is just treated as a.n.other region.

I've still got a few more pieces to handle which are listed in the todos so this is strictly WiP - I'm happy to get general comments but I'd suggest not diving into this too deeply as it might be subject to change. I'm putting the PR up in any case as this is a large change so getting an early look is probably useful.