Address implcity wants valid address

[MitchTurner]

This is confusing, so maybe we just bite the bullet and force all addresses to be valid. It's just been nice to put Address::new("alice") into tests and not have to think about it being correct. But since some of our impls take a dep on Address and do in fact expect a certain shape, we kinda need to do something. Specifically, the test clients are affected. The live clients kinda force you into us real addresses, whereas in the test code, it'll just give you weird errors when it tries to convert into bytes and stuff.

We can do better.