Dedicated server documentation is inaccurate for 4.0

**Your Godot version:**
4.0

**Issue description:**

I was trying to set up a new Godot 4.0 project that will use a dedicated game server and while going through the docs I realized that this page needs a bit of an overhaul. As a preface, the `server` platform was removed from SCons in the following PR and I believe that as a result, any reference to server vs. headless in the documentation is no longer accurate:

https://github.com/godotengine/godot/pull/49074

If I understand that pull request correctly, there is no longer a dedicated server binary and instead any platform can use the `--display-driver headless` argument.

The [Exporting for dedicated servers](https://docs.godotengine.org/en/stable/tutorials/export/exporting_for_dedicated_servers.html) probably needs a major rework. Some specific issues:
- It links to [server downloads page](https://godotengine.org/download/server) which 404s
- I believe this is because server binaries are no longer being built in 4.0 so this downloads page was taken down
- The `"Headless" vs "server" binaries` section is no longer valid
- It refers to the `godot-server` binary
- `./godot-server --main-pack my_project.pck`

It seems like the entire workflow for dedicated servers is probably different now? I think a relatively simple recommended flow could be something like:
- Add an option like `--server` to the user's project to be parsed with `OS.get_cmdline_user_args()` that should be handled such that the project will behave like a server
- Export a `.PCK` file (Same as before)
- Run the exported `foo.pck` file via `godot --display-driver headless --main-pack foo.pck -- --server`
- This `godot` executable is the same editor executable for the desired platform

Also, this [Introduction to the buildsystem](https://docs.godotengine.org/en/stable/contributing/development/compiling/introduction_to_the_buildsystem.html) page still refers to the `server` platform.

I don't mind submitting a PR for these but would like to first verify what the recommended solution is for dedicated servers in 4.0 so I don't write anything inaccurate.

**URL to the documentation page:**

- https://docs.godotengine.org/en/stable/tutorials/export/exporting_for_dedicated_servers.html
- https://docs.godotengine.org/en/stable/contributing/development/compiling/introduction_to_the_buildsystem.html