Allow Vue islands to be nested

### Description 📖

In some use cases it can be convenient to ignore client directives when an ancestor component is already an island.

An example from [this thread](https://github.com/ElMassimo/iles/issues/128#issuecomment-1189839536):

```
- EventContent
- EventDetails (client:load)
- NewsSubscription
- EmailSubscription (client:load)
```

and

```
- EventsContent
- NewsSubscription
- EmailSubscription (client:load)
```

### Implementation Details ⚙️

During page generation, it would be necessary for `Island` to `provide` a context, which can be detected by nested islands, to avoid rendering an additional client-side script and instead simply render the inner component.

Additionally, when building the client bundle, it would be necessary to replace [`Island`](https://github.com/ElMassimo/iles/blob/main/packages/iles/src/client/app/components/Island.vue) with a no-op implementation, to avoid injecting an additional script to hydrate that inner component.

Further discussion is needed to understand the impact on style extraction, and whether these two changes are actually implementable.