Mutability issues

[AlixANNERAUD]

Similar to issue #75, some references are marked as immutable even though the underlying objects are modified. For example, in Function::call, Instance is marked as immutable, but it's unlikely that Instance is only being read when a function is called.

[lum1n0us]

I suppose the main reason is that the rust-sdk is essentially a set of wrappers around wamr-sys, which is based on the C implementation. Unless we're copying the contents of a struct between Rust and C, rather than passing a C object between C functions from Rust, it can't be done easily and thoroughly.

[AlixANNERAUD]

Yeah, I don't really see how to achieve that...