core, network: Add ability to proxy socket packets

[FearlessTobi]

This is the second part of a series of Pull Requests, aiming to bring multiplayer functionality to yuzu. It adds the ability to proxy packets coming from our BSD socket implementation and therefore makes it possible to play "LAN-supported" games over the internet, without the need for external programs like Hamachi. For routing it introduces the concept of "fake" ip-addresses. It is needed in order not to leak the users local ip-address and to make multi-instance multiplayer on the same device possible.

The Pull Request also adds the dedicated-room build-target to make it easy for users to host their own server on either a local machine or a VPS.

Thanks a lot, especially to @german77 for helping me out a lot, @lat9nq for making the code compatible with Linux and everyone who helped me test the feature.

Please note that an LDN implementation is not part of this Pull Request.

[unuruu5760]

Local play still not working in luigi's mansion 3 scarescraper.