[Identity] Add tracing to the Identity service

Summary: Tracing provides structured logging and diagnostics info. It's especially helpful for asynchronous programs where log lines for various tasks can get intermixed.

Test Plan: Checked that detailed error logs appeared in my terminal

Reviewers: jimpo, atul, karol-bisztyga, palys-swm, geekbrother, ashoat

Reviewed By: karol-bisztyga, palys-swm, ashoat

Subscribers: ashoat, Adrian, yayabosh

Differential Revision: https://phabricator.ashoat.com/D3852