Feature request - native sandbox function call

I feel like making one binary that maps COW to both host and guest would be cool, that way the sandboxed function can be compiled to the same binary and a call to the function can be done in a native way without a string name but rather by:
```
#[sandboxed]
fn calculate(){}
guest.call(calculate)
```

How does that sound?

The issue names no files, tests, or entry points. Start by mapping the existing sandbox function-call API and the proposed COW host/guest arrangement, then determine whether the #[sandboxed] and guest.call(calculate) interface is feasible. Done would require an agreed design and an implemented native-call path with tests.

Scritto dal modello di indicizzazione a partire dal testo della issue.