Add component model example and add test in CI

[jsturtevant]

partially address hyperlight-dev/hyperlight#645

fixes #652
fixes #74

This pull request introduces support for WASI (WebAssembly System Interface) samples in the project. The changes include adding new functionality for compiling and running WASI examples, updating dependencies, and modifying build scripts and documentation to reflect the new features.

Component model example Implementation:

• New WASI Sample Module: Added a new wasi_samples module with necessary configurations in Cargo.toml, bindings, and implementation for WASI-specific functionality. This includes the example.wit interface defining adder and host functionalities, which are implemented in src/wasi_samples/src/lib.rs. [1] [2] [3]
• Example Application: Created a new example application (wasi_examples/main.rs) demonstrating the use of WASI bindings and sandboxing. It includes host and guest function implementations for WASI.

Build System Updates:

• Build Script Enhancements: Updated the Justfile to include commands for building and testing WASI examples (build-rust-wasi-examples, examples-wasi). This ensures proper handling of WASI imports and targets. [1] [2] [3]

Documentation Updates:

• Prerequisites: Updated the README.md to include installation instructions for wasm-tools and cargo component, which are required for WASI support. [1] [2]

Bug fixes

fixes #74 issue when host function with no return type is invoked by making the return value optional

[marosset]

LGTM except for some nits on naming and installing tools in the various just commands.

[marosset]

LGTM - thanks for making the changes to the just file!