5599: Add support for Rust code in DDNet r=def- a=heinrich5991
The glue is done using the [cxx crate](https://cxx.rs/) on the Rust side.
As a proof-of-concept, only a small console command (`rust_version`) printing the currently used Rust version was added.
You can generate and open the Rust documentation using `DDNET_TEST_NO_LINK=1 cargo doc --open`.
You can run the Rust tests using `cmake --build <build dir> --target run_rust_tests`, they're automatically included in the `run_tests` target as well.
Rust tests don't work on Windows in debug mode on Windows because Rust cannot currently link with the debug version of the C stdlib on Windows: https://github.com/rust-lang/rust/issues/39016.
---
The stuff in `src/rust-bridge` is generated using
```
cxxbridge src/engine/shared/rust_version.rs --output src/rust-bridge/engine/shared/rust_version.cpp --output src/rust-bridge/engine/shared/rust_version.h
cxxbridge src/engine/console.rs --output src/rust-bridge/cpp/console.cpp --output src/rust-bridge/cpp/console.h
```
Co-authored-by: heinrich5991 <heinrich5991@gmail.com>
The glue is done using the [cxx crate](https://cxx.rs/) on the Rust
side.
As a proof-of-concept, only a small console command (`rust_version`)
printing the currently used Rust version was added.
You can generate and open the Rust documentation using
`DDNET_TEST_NO_LINK=1 cargo doc --open`.
You can run the Rust tests using `cmake --build <build dir> --target
run_rust_tests`, they're automatically included in the `run_tests`
target as well.
Rust tests don't work on Windows in debug mode on Windows because Rust
cannot currently link with the debug version of the C stdlib on Windows:
https://github.com/rust-lang/rust/issues/39016.
---
The stuff in `src/rust-bridge` is generated using
```
cxxbridge src/engine/shared/rust_version.rs --output src/rust-bridge/engine/shared/rust_version.cpp --output src/rust-bridge/engine/shared/rust_version.h
cxxbridge src/engine/console.rs --output src/rust-bridge/cpp/console.cpp --output src/rust-bridge/cpp/console.h
```
Sort the stuff alphabetically, add some comments, ignore stuff that can
appear in build directories, so we don't have to guess the build
directory's name.
On Linux, `install` installs DDNet into the normal file system (root
rights required).
`package` tries to create an archive similar to today's release archives
and `package_source` tries to create a source archive similar to today's
source archives.
This system can easily be extended by independent authors without
collisions, something the old system with plain increasing integers did
not allow.
Do this by utilizing the previously unused message code `NETMSG_NULL`
which has a value of 0.
This works for engine and game messages, snapshot items and events.