lsp: Add default communication via stdout/stdin

[flofriday]

Currently the TCP port is hard-coded which means that on each machine only a single instance of the LS can be running.
Even with the option to specify the port, we're moving the problem the problem just a bit up because then we'll have to implement strategies for port choosing and recovery if the chosen port is already in use.

Many LSPs avoid this set of problems all together by using stdout/stdin as the communication for the protocoll and stderr exclusively for the logs.

It's probably still a good idea to leave in the option for a communication via TCP for development ergonomics.

Example: Gleam LSP

The gleam compiler comes with a build in LSP and starting it looks like:

As you can see it prints a short message (to stderr) and then waits in a loop for LSP messages via stdin.
I'm particularly found of this message and I think we should implement something similar.

Sidenote: I also like that it comes with the same binary as it makes packaging the lsp much easier but that will be problem for a future issue.

[Jozott00]

I agree that we should keep stdout/in clean and only use stderr for logs.

Regarding the port problem: if the user does not specify a certain port, we could use an arbitrary available one and just print the used port to the user.

[flofriday]

Yes, but since using stdout/stdin is the most common approach for LSPs and solves all port allocation issues I think it's the smartest move to just go with that and only use the port if specified.
Or am I missing something?

[Jozott00]

Yeah, if that is what most other real world LSPs are doing, we should do it too.