fix: session replay respect feature flag variants

[marandaneto]

:bulb: Motivation and Context

JS PR https://github.com/PostHog/posthog-js/pull/1040/

:green_heart: How did you test it?

:pencil: Checklist

• [x] I reviewed the submitted code.
• [x] I added tests to verify the changes.
• [ ] I updated the docs if needed.
• [x] No breaking change or entry added to the changelog.

[marandaneto]

@pauldambra would you mind taking a look? since I will need to implement this across SDKs

[marandaneto]

@ioannisj @pauldambra done, please double check after changes, I will do Android next (Monday)