fix: use String class for imported interface modules

[dOrgJelli]

Using a lifetime for the interface module became quite cumbersome when working on the ethereum wrapper. This is because when an object w/ an internal lifetime is used, that lifetime must be annotated upward in the definition hierarchy. This causes a very unpleasant developer experience where you must annotate a lot of types with the <'a> lifetime.

For example, please consider the following code:

pub fn get_interface() -> InterfaceModule<'a> {
    let impls = Interface::get_implementations();
    IProviderModule::new(impls[0].as_str())
}

struct SomeObject<'a> {
  interface_module: InterfaceModule<'a>;
}

impl SomeObject<'a> {
  ...
}

fn function<'a>(arg: &InterfaceModule<'a>) -> void {
  ...
}

The use-case that shined light on this: https://github.com/polywrap/ethereum/blob/main/wrapper/src/polywrap_provider/iprovider.rs

Changing the imported interface to use the String class is much more ergonomic.