Cannot add condition to aws_sns_subscriptions

I would like to be able to add conditions to subscriptions.

### Use Case

The use case here is that we want to add subscriptions only on some environments. For example, I want to add SMS subscriptions to an alarm topic only on productiolike environments.

### Proposed Solution

```
subscription = aws_sns_subscriptions.LambdaSubscription(function)
subscription.bind(topic)
subscription.node.default_child.cfn_options.condition = condition
```

### Other

* [x] :wave: I may be able to implement this feature request
* [ ] :warning: This feature might incur a breaking change

---

This is a :rocket: Feature Request

Start at the aws_sns_subscriptions entry point, particularly LambdaSubscription and the proposed subscription.node.default_child.cfn_options.condition usage. Trace how subscriptions are synthesized and identify existing tests for subscription resources. Done means conditions can be applied to subscriptions for selected environments without breaking existing subscription behavior.

Written by the indexing model from the issue text.