Consider using `wasm32-wasip2` target to build pure Rust programs

Now we are using `wasm32-wasip1` target to build pure Rust programs in `cargo-miden`. The frontend "wraps" the translated core Wasm module in the synthetic IR component.

Consider adding support in the frontend for pure Rust programs to be compiled as Wasm components ('wasm32-wasip2') for the following reasons:

- To unify the pure Rust program and rollup code handling in the frontend;
- Eventually `wasm32-wasip1` will be sunsetted, and we would need to switch to `wasm32-wasip2` anyway.