adding rust ADBench version

[ZuseZ4]

Usage for Rust side

export ENZYME_LOOSE_TYPES=1

cargo +enzyme run --release Comipling a lib.so to use from C: cargo +enzyme rustc --release --lib --crate-type=cdylib

[ZuseZ4]

Usage instruction: cargo +enzyme build fails with

  todo - hook in rust allocation fns
  UNREACHABLE executed at /h/344/drehwald/prog/rust/src/tools/enzyme/enzyme/Enzyme/GradientUtils.cpp:9107!

https://github.com/EnzymeAD/Enzyme/blob/880fb3272e4e34a8535a36f0d0a0fb232630a2b9/enzyme/Enzyme/GradientUtils.cpp#L9136

[ZuseZ4]

printing the module before AD (with a few helping infos at the end) err.ll.txt