[native_rust_library] Extend findUserIdentities response
Summary:
Modified native_rust_library code to process the new response field. JS changes are made in the next diff.
Depends on D12924
Test Plan: Played with useFindUserIdentities() and made sure it still works as expected.
Reviewers: varun
Reviewed By: varun
Subscribers: ashoat, tomek
Differential Revision: https://phab.comm.dev/D12925