Enable Exit Policy by Autonomous System Numbers

This ticket is to improve Tor in a way to enable Exit Policy to be able to accommodate AS numbers, other than just IP addresses/netblocks and ports.

This requirements come up when measuring how to make a Tor Exit Relay that enable connections only to high traffic, but very likely not abuse-generating, websites of major internet destinations.

Assuming that i may wish to make a Tor Exit nodes only for those destinations where we know there's high traffic to be routed trough the Tor Network, but with a limited risks of ISP/Provider takedown due to those large corporations not being automatic-abuse-generating, i tried to collect the numbers of AS for each of the following: Google (17 AS) Facebook (1 AS) Twitter (3 AS) Microsoft (28 AS) Yahoo (59 AS) Wikipedia (3 AS) Linkedin (9 AS) Github (1 AS) Cloudflare (5 AS)

The amount of netblocks part of those AS are a lot and i don't think they will fit the Exit Policy. When it has been tried to load the list of all Italian netblocks (like at legacy/trac#993 (moved)), weird things happened and it basically didn't worked out.

If Tor servers and clients would become AS-aware, then it would be possible to run a Tor Exit node, deciding to refine an exit policy for very-limited-liability and very-limited-abuse-generating-setup that could probably make it easier to run Tor also on my home broadband line (not being abuse generating destinations, my home ISP won't cut me the subscription!).

That's something that could become a brick of a building block to reach a point where the end-user (Tor Browser users) maybe able to route some traffic out by default (ex: route only the top target AS destinatation that would dynamically enable to offload the "bulk-but-not-abuse-generating" network traffic)