[lib] Move pendingThreadIDRegex to validation-utils.js

Summary: Solution for ENG-4835

Test Plan: Check if all files import pendingThreadIDRegex from validation-utils.js and if error doesn't appear on web.

Reviewers: michal, inka, bartek, tomek

Reviewed By: bartek

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D9067