[lib] Inline reduceDeviceToken

Summary:
issue: https://linear.app/comm/issue/ENG-5652/inline-reducedevicetoken
See the deleted file for how it worked before

Test Plan: Dispatched incrementalStateSyncActionType, setDeviceTokenActionTypes actions, chcked that the state changes as expected

Reviewers: michal, kamil, ginsu

Reviewed By: michal

Subscribers: ashoat, tomek, wyilio

Differential Revision: https://phab.comm.dev/D9816