Codechange: workaround CMake/Xcode duplicate file name issue (#11186)

Having a library with files with the same name isn't supported in CMake's Xcode project file generation: https://gitlab.kitware.com/cmake/cmake/-/issues/20501. One of the files is renamed to work around this bug.

Codechange: Swap SocketList map key/value around.

This map is used store socket and address together, and, other than
checking that the address does not already have a socket, the data layout
does not seem particularly important.

However, as address is the key, technically it should not be modified,
and address may self-modify itself during comparisons.

Codechange: [Network] split CloseSocket and CloseConnection more clearly (#9261)

* Codechange: [Network] split CloseSocket and CloseConnection more clearly

- CloseSocket now closes the actual OS socket.
- CloseConnection frees up the resources to just before CloseSocket.
- dtors call CloseSocket / CloseConnection where needed.

Change: reworked the debug levels for network facility (#9251)

It now follows very simple rules:
0 - Fatal, user should know about this
1 - Error, but we are recovering
2 - Warning, wrong but okay if you don't know
3 - Info, information you might care about
4 -
5 - Debug #1 - High level debug messages
6 - Debug #2 - Low level debug messages
7 - Trace information

Codechange: move all NetworkGameInfo related functions to a single file

It currently was a bit scattered over the place. Part of
NetworkGameInfo is also the GRF Identifiers that goes with it.

Remove: "language" field from server/client

The original idea was that people could find a server they could
talk in their native language on. This isn't really used in that
way. There are several reasons for removing this:

- the client also sends his "language" to the server, but nothing
is doing anything with this.
- flags are a bad way to represent languages, and over the years
we had several (rightfully) complaints about this.
- most servers have their language set to "All", and prefix the
servername with the language it is about. This is a much more
efficient way to do the same.

All in all, this feature should go back to the drawing board.
Maybe it could work in another form, but this form is not it.

Remove: "map_name" from server announcements / listing

The idea back in the days was nice, but it never resulted in
anything useful. Most servers either read "(loaded game)" or
"Random Map", neither being useful. It was meant for heightmaps,
so you could find a server that was using a specific one .. but
there are many things wrong with that idea. Mostly, servers tend
to save and load savegames from time to time, after which the
original heightmap used was lost.

All in all, removing map_name all together is just better.

Fix: Thread unsafe use of NetworkAddress::GetAddressAsString

Remove static buffer form of NetworkAddress::GetAddressAsString.
This is used in multiple threads concurrently, and is not thread-safe.

Replace it with a form returning std::string.

Remove: ENABLE_NETWORK switch

This switch has been a pain for years. Often disabling broke
compilation, as no developer compiles OpenTTD without, neither do
any of our official binaries.

Additionaly, it has grown so hugely in our codebase, that it
clearly shows that the current solution was a poor one. 350+
instances of "#ifdef ENABLE_NETWORK" were in the code, of which
only ~30 in the networking code itself. The rest were all around
the code to do the right thing, from GUI to NewGRF.

A more proper solution would be to stub all the functions, and
make sure the rest of the code can simply assume network is
available. This was also partially done, and most variables were
correct if networking was disabled. Despite that, often the #ifdefs
were still used.

With the recent removal of DOS, there is also no platform anymore
which we support where networking isn't working out-of-the-box.

All in all, it is time to remove the ENABLE_NETWORK switch. No
replacement is planned, but if you feel we really need this option,
we welcome any Pull Request which implements this in a way that
doesn't crawl through the code like this diff shows we used to.

Remove: BeOS support (deprecated by Haiku)

In 10 years there is no commit to change how BeOS works, and we
have no active maintainer for it. It is unlikely it works in its
current state (but not impossible).

With the arrival of SDL2 (and removal of SDL), BeOS is no longer
support. SDL2 suggests to use Haiku instead of BeOS.

(svn r8361) -Codechange: make sure the range of the dates coming from the network are valid in OpenTTD
-Codechange: use_password is a boolean variable
-Codechange: move range checking for server_lang and map_set to Recv_NetworkGameInfo