[lib] Destructure some properties in reduceThreadInfos to improve readability

Summary:
Super minor noop refactor. Thought destructuring some properties would make things a little more readable.

Depends on D4198

Test Plan: Noop

Reviewers: palys-swm, def-au1t

Reviewed By: palys-swm

Subscribers: ashoat, Adrian, yayabosh

Differential Revision: https://phab.comm.dev/D4200