feat(agent): add guest agent with rust support

[mmoreiradj]

What am I looking at ?

• add a workload runner that configures itself from a file
• add an agent trait for languages to be easily implemented
• supports rust
• no communication with vmm YET

How do I test it ?

For now, we didn't add the code to test it inside the vm, so you can run it by editing

build.source-code-path at src/agent/examples/config.toml

And then running

cargo run --bin agent -- --config=./src/agent/examples/config.toml