Add Rust binary examples and compilation support

[danbugs]

Add Rust example programs that compile to Nanvix binaries and document the compilation process. Current binary support works for C/C++ but Rust compilation succeeds but runtime execution fails with socket errors. Need to investigate Rust-specific runtime requirements, add working Rust examples to guest-examples/, and document the cargo compilation workflow using the nanvix target. Should include simple and complex Rust programs demonstrating std library features.

Repro:

cd guest-examples/
cargo new hello-rust
docker pull nanvix/toolchain:latest
docker run --rm -v "$(pwd):/mnt" -v "$HOME/.cache/nanvix-registry:/nanvix-registry:ro" nanvix/toolchain:latest /bin/bash -l -c 'cd /mnt && cargo +nanvix-x86 build --release --target i686-unknown-nanvix'
cp hello-rust/target/i686-unknown-nanvix/release/hello-rust.elf hello-rust.elf
cargo run -- guest-examples/hello-rust.elf

Output:

    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.11s
     Running `target/debug/hyperlight-nanvix guest-examples/hello-rust.elf`
Error running workload: failed to connect to gateway socket (address=/tmp/hyperlight-nanvix/nvx:hello-rust.elf:gw-2856724221.debug.socket)