[services] Tunnelbroker - Refactor time types

Summary:
We want to change long long to int64_t to be sure about the size of variables(long basically might be compiler-dependent).

https://linear.app/comm/issue/ENG-584/refactor-time-types-in-c

Test Plan:

cd services
yarn run-tunnelbroker-service

Reviewers: geekbrother, palys-swm

Reviewed By: geekbrother, palys-swm

Subscribers: ashoat, palys-swm, Adrian, atul, benschac, yayabosh

Differential Revision: https://phabricator.ashoat.com/D3711