C binding: wasi std out to string

#### Feature

Rust library can bind WritePipe to WasiCtx stdout which can be far simpler and effective than OS files went dealing with multiple short-lived instances.

It is not currently possible with C/C++ bindings

#### Benefit

- Avoid useless error-prone and slow interactions by filesystem
- Allow simpler integration in freestanding targets

#### Implementation

Leverage existing [wasi_common](https://docs.rs/wasi-common/0.38.1/wasi_common/index.html)::[pipe](https://docs.rs/wasi-common/0.38.1/wasi_common/pipe/index.html)::[WritePipe](https://docs.rs/wasi-common/0.38.1/wasi_common/pipe/struct.WritePipe.html#) and ReadPipe on the rust side to implemented a binding in `c-api` crate.

#### Alternatives

Export some basic filesystem operations in c binding