Change the injection count of fuel in a store from u32 to u64 (#3048)

* Change the injection count of fuel in a store from u32 to u64

This commit updates the type of the amount of times to inject fuel in
the `out_of_fuel_async_yield` to `u64` instead of `u32`. This should
allow effectively infinite fuel to get injected, even if a small amount
of fuel is injected per iteration.

Closes #2927
Closes #3046

* Fix tokio example

tests/all/async_functions.rs

@@ -392,7 +392,7 @@ fn iloop_with_fuel() {
 fn fuel_eventually_finishes() {
     let engine = Engine::new(Config::new().async_support(true).consume_fuel(true)).unwrap();
     let mut store = Store::new(&engine, ());
-    store.out_of_fuel_async_yield(u32::max_value(), 10);
+    store.out_of_fuel_async_yield(u64::max_value(), 10);
     let module = Module::new(
         &engine,
         "