Add Socket for standalone server

[trickymagus]

Currently, the scrcpy-server uses LocalSocket for communication.
However, when attempting to run the scrcpy-server as a standalone server and connect to the LocalSocket through another android application, a permission error occurs.
We can add the capability to use Socket instead of LocalSocket, allowing other applications to communicate with the scrcpy-server.

[rom1v]

Hi,

Although scrcpy-server exposes some options to simplify using it as a standalone server (because "why not"), their implementation is trivial and non invasive.

Its primary purpose is still to serve the scrcpy client. I don't want to expose unrelated features just for external usages of scrcpy-server as a standalone server (it brings more complexity, more code to maintain, untested code…).

[Tryanks]

I believe this is not a good design, which adds unnecessary complexity and redundant branching judgments to the program. In order to implement Socket support, I'd be inclined to implement a Socket wrapper to provide a unified interface, and subsequently implement Socket and LocalSocket separately within it. however, your code contribution here is definitely a good enough PoC.