[tg bot] Improve msg sending tests

Summary:
T2972

Depends on D13416

Allow app to store a tg bot for local testing and for prod, so that local testing will not shut down a prod instance

Test Plan: npm run msgs and all send

Reviewers: #bitcoin_abc, emack

Reviewed By: #bitcoin_abc, emack

Differential Revision: https://reviews.bitcoinabc.org/D13417