Use "socket:/path/to/socket" syntax everywhere for AF_UNIX ports

With #11485 (moved), Andrea did a cool syntax for AF_UNIX hidden-service address targets.

Why didn't all the other FooPort options think of that?

We shouldn't have a separate option for Unix vs IP address as in:

SocksPort 127.0.0.1:9050
SocksSocket /home/nickm/.tor/connect-to-this

Instead why not just have it be:

SocksPort 127.0.0.1:9050
SocksPort socket:/home/nickm/.tor/connect-to-this