[native] Clear auth metadata on logout
Summary:
When a user logs out, we need to clear the auth metadata. This requires adding a function that is responsible for clearing the metadata and emitting new values.
We're setting empty strings as new metadata - which isn't ideal. We're going to improve it as a part of https://linear.app/comm/issue/ENG-7657/improve-auth-metadata-handling.
Depends on D11534
Test Plan: Log out and check if an event with empty token was emitted
Reviewers: kamil, inka, varun, ashoat
Reviewed By: varun, ashoat
Subscribers: marcin, ashoat
Differential Revision: https://phab.comm.dev/D11573