[sdk-platform-java] Make ServerStream support spliterator()

**Affects :** 1.58.2

`ServerStream` currently doesn't allow to call the `iterator()` method more than once. However some tool that consumes this iterable may want to check the characteristics. E.g the reactor project (webflux) which is now checking the characteristics of the iterator via `Iterable.spliterator()`. However this has the side effect of invoking the default method which invokes the `iterator()` method, thus setting the `consumed` boolean to `true`.

_FluxIterable_
```java
static boolean checkFinite(Iterable iterable) {
return iterable instanceof Collection || iterable.spliterator().hasCharacteristics(Spliterator.SIZED);
}
```

_Iterable_
```java
default Spliterator spliterator() {
return Spliterators.spliteratorUnknownSize(iterator(), 0);
}
```

While this can be worked around for this particular use case, it would be nice if the `ServerStream` provide basic support for spliterators.