Unify the TCP socket over Qrexec method

[ben-grande]

Current problem (if any)

There are various ways a client connects:

• qvm-connect-tcp
• qrexec-client-vm systemd service with matching socket
• socat executing qrexec-client-vm in systemd service

There are various ways a server is connected:

• scoat with unix sockets
• qusal.ConnectTCP, similar to old script qubes.ConnectTCP and the new functionality of it but allows remote hosts with socat
• qusal.Ssh, qusal,Rsync, qusal.Syncthing etc, which are wrappers around qubes.ConnectTCP

The many methods brings confusion on what should be implemented.

Proposed solution

1. Decide the best method for each case.
2. Code only in allowed methods.
3. Document allowed methods.

The value to a user, and who that user might be

Clearly decide on the best method and follow a standard. Easier for developers to grasp the codebase and for users to build upon.

.