[native] Use MMKV locking utils to sync between main app and notifs code

Summary: This differential implements synchronization that ensures encryption always wins against decryption on native notifs.

Test Plan:

1. Navigate to the top of this stack.
2. Apply this patch: https://gist.github.com/marcinwasowicz/c89b5c944e6336a6d366895327accb51
3. Build native app and web app.
4. Try sending messages back and forth between both apps making.
5. Examine the main app and the NSE logs. Main app should always persist notifs data while the NSE should sometimes fail to persist.

Reviewers: kamil, bartek

Reviewed By: bartek

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D13008