Stop all integrations like session replay and autocapture on opt-out

### Description

Original discussion: https://github.com/PostHog/posthog-ios/pull/276#discussion_r1905431037

When opting-out, we should `stop()` all integrations since they won't be processed by the SDK, and then `start()` again on next opt-in. 

For session replay, when opting-in a new session should be created.

- [ ] iOS
- [ ] Android
- [ ] React Native
- [ ] Flutter