[identity] Use DB error types from comm-lib

Summary:
The DBItemError and DBItemAttributeError were defined both in Identity and comm-lib, however their signatures differ slightly.
Replaced the definitions in Identity with the ones from comm-lib, made slight modifications (added From derive) to make them compatible.
This isn't perfect and is kind of messy, but will be reworked later.

Depends on D10446

Test Plan: Identity compiles, tests pass.

Reviewers: varun, michal

Reviewed By: michal

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D10447