Implement ChangeThreadSubscriptionSpec and add ThreadSubscription to createThickRawThreadInfo

Summary: This differential implements DMOperation and necessary spec for changing thread subscription. Additionally createThickRawThreadInfo is modified to accept information about subscription. This way users will get to now other members subscriptions when they are added or join the thread.

Test Plan:

1. Apply this patch: https://gist.github.com/marcinwasowicz/e0e48311f76df2acbacd0ac59e888a9c
2. Send message from one web user to another.
3. Ensure that both have new thread in redux and the sender has non-default subscription.

Reviewers: tomek, kamil

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13132