[identity] Rewrite GetDeviceLists RPC to use batch functions

Summary:
Final part of GetDeviceListsForUsers RPC rewrite. Details in ENG-8843.

Replaced old implementation with a new one that uses batch functions introduced in D12888 and D12889.

Depends on D12889

Test Plan: Detailed test plan in ENG-8843.

Reviewers: varun, will, kamil

Reviewed By: varun

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D12890