Implement RFC 11: Redesigning Wasmtime's APIs (#2897)

Implement Wasmtime's new API as designed by RFC 11. This is quite a large commit which has had lots of discussion externally, so for more information it's best to read the RFC thread and the PR thread.

examples/gcd.rs

@@ -10,13 +10,13 @@ fn main() -> Result<()> {
     // Load our WebAssembly (parsed WAT in our case), and then load it into a
     // `Module` which is attached to a `Store` cache. After we've got that we
     // can instantiate it.
-    let store = Store::default();
+    let mut store = Store::<()>::default();
     let module = Module::from_file(store.engine(), "examples/gcd.wat")?;
-    let instance = Instance::new(&store, &module, &[])?;
+    let instance = Instance::new(&mut store, &module, &[])?;
 
     // Invoke `gcd` export
-    let gcd = instance.get_typed_func::<(i32, i32), i32>("gcd")?;
+    let gcd = instance.get_typed_func::<(i32, i32), i32, _>(&mut store, "gcd")?;
 
-    println!("gcd(6, 27) = {}", gcd.call((6, 27))?);
+    println!("gcd(6, 27) = {}", gcd.call(&mut store, (6, 27))?);
     Ok(())
 }